U.S. patent application number 14/214716 was filed with the patent office on 2015-12-31 for trim method for high voltage drivers.
The applicant listed for this patent is David Schie, David Spady, Mike Ward. Invention is credited to David Schie, David Spady, Mike Ward.
Application Number | 20150381176 14/214716 |
Document ID | / |
Family ID | 54931632 |
Filed Date | 2015-12-31 |
United States Patent
Application |
20150381176 |
Kind Code |
A1 |
Schie; David ; et
al. |
December 31, 2015 |
TRIM METHOD FOR HIGH VOLTAGE DRIVERS
Abstract
Methods and circuits are provided to create small, power
minimizing, multi-channel high voltage drivers for
micro-electromechanical systems (MEMS). A resistor calibration
circuit is introduced to allow on chip resistor dividers to be
calibrated against a single precision high voltage resistor
divider, eliminating the cost and printed circuit board real estate
associated with multiple resistor dividers connected to each
channel. Additionally, a multiple-power rail configuration is
provided to reduce power to the overall system by producing several
rails generated by a boost converter or a capacitive charge pump,
where the voltage output of the rails is produced to group rails of
lesser voltage requirement rather than connecting all channels to
the same high voltage rail on a dynamic basis.
Inventors: |
Schie; David; (Cupertino,
TX) ; Ward; Mike; (Tallmadge, OH) ; Spady;
David; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schie; David
Ward; Mike
Spady; David |
Cupertino
Tallmadge
San Jose |
TX
OH
CA |
US
US
US |
|
|
Family ID: |
54931632 |
Appl. No.: |
14/214716 |
Filed: |
March 15, 2014 |
Current U.S.
Class: |
327/108 ;
327/541 |
Current CPC
Class: |
H03K 19/0005 20130101;
G05F 3/02 20130101 |
International
Class: |
H03K 19/00 20060101
H03K019/00; H03K 17/16 20060101 H03K017/16; H02M 3/07 20060101
H02M003/07; H03K 5/24 20060101 H03K005/24 |
Claims
1. An integrated circuit driver for driving at least one accurate
high-voltage outputs comprising: at least one high voltage driver
channel output terminals; an external precision high impedance
resistor divider coupled externally to said at least one high
voltage divider channel output terminals; an internal resistor
divider coupled to said at least one high voltage divider output
terminals; and a resistor calibration circuit; wherein said one or
more internal resistor dividers are calibrated in conformance with
said external precision high impedance resistor divider until a
voltage on a set of divider taps match.
2. The integrated circuit driver of claim 1, wherein said resistor
calibration circuit comprises: a high impedance on chip resistor
divider; a window comparator coupled to said external precision
high impedance resistor divider and said internal resistor divider;
and a voltage source output or pair of mirrored current source
outputs whose magnitude conforms to a command from a controller,
said voltage source output or said pair of mirrored current source
outputs coupled to said internal resistor divider and said external
precision high impedance resistor dividers; wherein internal
resistors are modified in conformance with said window comparator
output to increase a tap point voltage or reduce the tap point
voltage until the voltage on the internal resistor divider equals
the voltage on the tap point of the external precision high
impedance resistor divider as indicated when the voltage is within
the hysteresis band of said comparator.
3. The integrated circuit driver of claim 2, wherein said window
comparator has a positive magnitude output for increment, a
negative magnitude output for decrement, and an intermediate
magnitude output for equal or near equal voltage magnitude.
4. The integrated circuit driver of claim 1, wherein said resistor
calibration circuit comprises: an internal high impedance
monolithic resistor divider whose value is established by digital
means; a window comparator coupled to said external precision high
impedance resistor divider and said internal high impedance
monolithic resistor divider; said precision external resistor
divider; and a voltage or pair of matched current sources with
programmable magnitude coupled to a command input and to each of
said internal and external resistor dividers, where said magnitude
is adjusted in conformance with said input command to produce a
command voltage on the external resistor divider; wherein said
window comparator compares the voltage on the external precision
high impedance resistor divider and said internal resistor dividers
and increments or decrements the value of the internal resistor
divider magnitude until two tap voltages match within the window
comparator window (hysteresis).
5. (canceled)
6. (canceled)
7. The integrated circuit of claim 1 further comprising: at least
one high voltage rail coupled to said high voltage driver channel
output terminals; at least one high voltage power rail generator; a
controller coupled to said at least one high voltage power rail
generators; and a high voltage multiplexer; wherein said power rail
voltages are dynamically established by said controller which
further groups channels to be coupled to a given high voltage rail
and then couples them to said given high voltage rail using said
high voltage multiplexer so as to minimize total system power
consumption.
8. The integrated circuit of claim 7 further comprising one or more
boost converters, said boost converters included
monolithically.
9. The integrated circuit of claim 8, wherein said boost converters
are created in a dielectrically isolated process to isolate its
switching noise from other circuits.
10. The integrated circuit of claim 7 further comprising at least
one charge pump stages, said at least one charge pump stages
included monolithically.
11. The integrated circuit of claim 10, wherein said at least one
charge pumps stages are created in a dielectrically isolated
process to isolate its switching noise from other circuits.
12. The integrated circuit of claim 7 further comprising a
sub-regulator so as to create a sub-regulated voltage for each
channel so as to isolate each channel from glitches associated with
at least one of changing the magnitude of the high voltage rails
and to produce output rails which conform to a maximum voltage that
can be accommodated by selected semiconductor devices.
13. The integrated circuit driver of claim 1 further comprising a
multiplexer connecting said external precision high impedance
resistor divider to said resistor calibration circuit.
14. The integrated circuit of claim 1, wherein said internal
resistor divider is multiplexed to said resistor calibration
circuit in a continuous or periodic pattern so as to continuously
calibrate said internal resistor divider.
15. The integrated circuit of claim 1, wherein said internal
resistor divider are multiplexed to said resistor calibration
circuit when commanded by an external controller provided either
directly to a terminal or through a digital bus.
16. A precision multi-channel monolithic voltage regulation circuit
comprising: a closed loop amplifier; a level shift; an internal
divider feedback network calibrated against an external precision
resistor divider; and wherein said closed loop amplifier couples a
voltage to an output terminal utilizing said level shift or said
transconductor in conformance with the calibrated internal divider
feedback network.
17. The integrated circuit of claim 7, wherein the at least one
high voltage power rail generator creates multiple rails using a
single switch and single feedback loop.
18. The integrated circuit of claim 10, wherein the at least one
high voltage power rail generator creates multiple rails using a
single switch and single feedback loop.
19. (canceled)
20. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of U.S. Provisional Patent
Application Ser. No. 61/786,310 filed Mar. 15, 2013, which is
incorporated herein by reference
FIELD OF THE INVENTION
[0002] The present invention in general relates to electronic
components and in particular to methods and circuits to create
small, power minimizing, multi-channel high voltage drivers for
micro-electromechanical systems (MEMS).
BACKGROUND OF THE INVENTION
[0003] Microelectromechanical systems (MEMS) is the technology of
very small devices, that merge at the nano-scale into
nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are
made up of components between 1 to 100 micrometers in size (i.e.
0.001 to 0.1 mm), and MEMS devices generally range in size from 20
micrometers (20 millionths of a meter) to a few millimeters (i.e.
0.02 to >1.0 mm). MEMS usually consist of a central unit that
processes data (the microprocessor) and several components that
interact with the surroundings such as microsensors. At these
sizes, the standard constructs of classical physics are not always
useful. Because of the large surface area to volume ratio of MEMS,
surface effects such as electrostatics and wetting dominate over
volume effects such as inertia or thermal mass.
[0004] MEMS are finding more and more applications in commercial,
industrial, military and medical markets. Today
microelectromechanical systems are used to drive such things as: i)
micro-mirror arrays for optical switching applications; ii)
piezo-electric transducers for ultrasound; iii) cholesteric
molecules for sensing and no-power display applications; iv)
gyroscopes; v) accelerometers; vi) radar and other switches; vii)
microfluidic pumps; viii) camera and eye lenses; ix) biological
microarrays; x) biological cells based sensors and transducers such
as heart cell actuators, and various other mechanical
assemblies.
[0005] While the applications for MEMS are as varied as the
imagination, many MEMS applications share a common requirement for
a high voltage interface IC or integrated circuit capable of
driving and/or interfacing and/or generating high voltage precision
waveforms with extreme accuracy, over large numbers of channels, in
an area not so large as to eliminate the benefits of the
microelectromechanical device whose primary benefit is usually to
save space and power so as to be incorporated into portable or
miniature products. They also are often deployed in applications
which operate from batteries or for which power must be minimized
and often the small size of the MEMs sensors produces a desire for
small form factors for the interfaces, biasing circuits, and power
supplies to be of practical use.
[0006] In most microelectromechanical systems, each high voltage
MEMS driver channel has a high impedance (to keep currents low)
resistor divider creating a low voltage tap point proportional to
the high voltage output. The feedback tap point is in turn coupled
to a precision amplifier, normally auto-zeroed or nulled, which in
turn drives a transconductor or level shift in a closed loop to
create an output on the driver channel in conformance with an
analog voltage or digital to analog (D/A) commanded input. The
command input could be from a digital interface, a voltage level, a
pulse-width modulation (PWM) input, or a similar input known to
those skilled in the art.
[0007] Unfortunately, high valued resistors of high precision and
with tight drift and temperature specifications and high initial
accuracy are very expensive and difficult to source. Furthermore,
arraying large numbers of high valued resistors across a printed
circuit board creates high impedance nodes which are sensitive to
noise coupling and leakage and uses a lot of space. Often these
noise sources are introduced by the switching power supplies,
usually boost converters, residing on or near the MEMS driver
circuitry. The result is that most MEMS drivers have poor accuracy,
"glitching problems," poor power characteristics, and are often
much larger than the MEMS devices they are trying to drive.
[0008] High voltage integrated circuits capable of coupling current
onto a high voltage output with multiple channels are available.
The high voltage integrated circuits accept either an analog input
or a digital input and can command an output. In general high
voltage integrated circuits either use internal resistors, in which
case their relative accuracy is poor, especially over the drift of
the process, or high voltage integrated circuits rely on an
external resistor divider for each channel. Even if multiple on
chip resistors are trimmed for good initial accuracy, a costly
process, their drift and voltage coefficient specification is still
relatively poor. Exotic materials like SiCr may be used, however,
on-chip thermal drift between the different channels, chip topology
and the drift of the material itself still do not meet the very
tight accuracy requirements of many MEMS drivers or make the cost
of such drivers prohibitive.
[0009] MEMs system which require multiple high voltage driver
outputs also require a means by which to create the rails to drive
those outputs. The power supplies required to generate high voltage
rails from a low voltage battery can often be extremely large often
requiring more than one stage due to the small duty cycle that
would otherwise be required. Finally, most implementations of these
power supplies are not monolithic and take up a great deal of
space. The high voltage driver outputs pull their current from the
highest voltage possible and therefore even if the required output
voltage is small the power consumed is not reduced.
[0010] It would therefore be desirable to create a multichannel
MEMS driver by which multiple channels in an integrated circuit may
be trimmed against a single external precision low-drift resistor
divider. Additionally, it would be desirable to incorporate the
high-voltage rail generation control and switching circuitry on the
integrated circuit to minimize electromagnetic interference (EMI)
and printed circuit board (PCB) loops which can radiate and to save
space. Finally, it would be desirable to be able to select rails
for multiple outputs on a dynamic basis in conformance with the
output voltage command so as to reduce the overall system power use
(where rails lower than a given rail are grouped, and the rail
sub-regulated to each channel). And finally, it would be desirable
to monolithically include all of these components to save space and
to utilize a dielectrically isolated process to isolate the power
converter switching noise from the rest of the circuitry (ie.
charge pumps and inductive boost converters).
SUMMARY OF THE INVENTION
[0011] Methods and circuits are provided to create small, power
minimizing, multi-channel high-voltage drivers for
micro-electromechanical systems (MEMS). A resistor calibration
circuit is introduced to allow on-chip resistor dividers to be
calibrated against a single precision high-voltage resistor
divider, eliminating the cost and printed circuit board real estate
associated with multiple resistor dividers connected to each
channel. Additionally, a multiple power rail configuration is
provided to reduce power to the overall system by producing several
rails generated by a boost converters and/or capacitive charge
pumps, where the voltage rails are produced to group outputs of
lesser voltage requirement rather than connecting all channels to
the same high voltage rail. The rails for each individual channel
can be selected dynamically as required.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention is further detailed with respect to
the following drawings. These figures are not intended to limit the
scope of the present invention but rather illustrate certain
attributes thereof.
[0013] FIG. 1 is a schematic of a closed loop amplifier gain
loop;
[0014] FIG. 2 is a schematic of a calibration circuit according to
an embodiment of the invention;
[0015] FIG. 3 is a schematic of a calibration circuit with a
multiple rail connection according to an embodiment of the
invention;
[0016] FIG. 4 is a schematic of a channel muxed to calibration with
a regulator between the input rail and channel according to an
embodiment of the invention;
[0017] FIG. 5 is a schematic of a complete multichannel MEMS driver
solution including internally generated multiple supply rails
according to an embodiment of the invention;
[0018] FIG. 6 is a schematic of a channel connected to one of
multiple supply rails according to an embodiment of the
invention;
[0019] FIG. 7 is a schematic of a resistor trim circuit according
to an embodiment of the invention; and
[0020] FIG. 8 is a schematic of a boost integrated circuit
configuration with charge pump stages according to an embodiment of
the invention.
DESCRIPTION OF THE INVENTION
[0021] The present invention has utility as improved methods and
circuits to create small, power minimizing, multi-channel high
voltage drivers for micro-electromechanical systems (MEMS). A
resistor calibration circuit is introduced to allow on chip
resistor dividers to be calibrated against a single, low drift,
precision, high-voltage resistor divider, eliminating the cost and
required printed circuit board real estate associated with multiple
resistor dividers connected to each channel. Additionally, a
multiple-power rail circuit configuration is taught to reduce power
to the overall system by producing several rails generated by a
boost converter and/or a capacitive charge pump, where the voltage
output of the rails is produced to group rails of lesser voltage
requirement rather than connecting all channels to the same high
voltage rail on a dynamic basis.
[0022] In embodiments of the invention, an integrated circuit
device is introduced where two or more high voltage outputs are
coupled to on chip resistor dividers. These resistor dividers,
however, are each continuously calibrated against a single external
low drift precision external resistor divider utilizing a novel
calibration technique which calibrates the resistor accuracy, and
calibrates out the effects of resistor leakage. The resulting
inventive solution removes large numbers of precision, expensive,
noisy and leakage prone external devices while overcoming the
accuracy and drift short comings of on chip resistors. An
embodiment of the inventive technique is described in more detail
below:
[0023] FIG. 1 is a prior art schematic of an amplifier in a closed
loop gain configuration. Operational amplifiers with resistive
feedback have long been recognized as one of the best ways to
amplify an analog signal. The operational amplifier configuration
of FIG. 1 is a non-inverting gain configuration. Assuming the
operational amplifier of FIG. 1 does not have an input offset
voltage, the output of this circuit is determined by equation
1:
V OUT = V IN ( 1 + R 2 R 1 ) ( 1 ) ##EQU00001##
[0024] In order to ensure the accuracy of the output, resistors R1
and R2 must be very accurate. This burden is heightened when the
ratio of R2 to R1 becomes large and when the output voltage,
V.sub.OUT becomes large. This is especially challenging when
integrating the feedback resistors onto an integrated circuit where
resistors usually have relatively high voltage-coefficients and
temperature-coefficients. One existing solution to this problem is
to use external R.sub.1 and R.sub.2 resistors and calibrate the
resistors to eliminate their matching errors. While this solution
can be successful, it requires two external resistors for each
channel, where the number of channels typically number in the tens,
hundreds or thousands. Also, this solution does not lend itself
well to integrating the feedback resistors onto an integrated
circuit as high quality, high-voltage integrated resistors are
rare. Furthermore, while this calibration method could be used with
integrated resistors, typically the voltage-coefficient and
temperature coefficients of integrated resistors would render the
calibration process excessively time consuming and complicated as
the number of calibration coefficients would be very large and must
be measured over both output voltage and system temperature. Based
on the aforementioned implementation obstacles, it would be
desirable to have an integrated solution with many amplifiers on
one die, whose integrated feedback resistors are calibrated in
real-time to one pair of external resistors. This would allow for a
significant component reduction while maintaining a high level of
system accuracy. FIG. 2 shows the inventive implementation of this
circuit.
[0025] FIG. 2 is a schematic of a channel connected coupled
calibration circuit 10 according to an embodiment of the invention.
Resistors R.sub.1 (12) and R.sub.2 (14) are the internal feedback
resistors. Resistors R.sub.3 (16) and R.sub.4 (18) are the external
resistors which R.sub.1 (12) and R.sub.2 (14) will be calibrated
to. The output voltage is created through (25) which represents a
voltage output but could also be a transconductor with mirrored
current output coupled into each of the resistor dividers. FIG. 2
further shows SI which may be extended to a multiplexer to the
calibration circuitry for a larger number of channels according to
an embodiment of the invention. FIG. 3 further shows an example of
three different power rails operating coupled to (25). The
selection of the voltage rail in FIG. 3 is determined by a
controller which sets the rail from the boost converter or charge
pump just above that required by the commanded voltage output.
[0026] The method of calibration is as follows:
1. Switch S1 is closed connecting the external resistors (16, 18)
to the output of the channel 20. 2. An auto-zero window comparator
22 is used to compare the tap point on the external resistors, V2,
with the internal feedback resistor tap point, V1. 3. Based on the
output of the comparator 22, the internal R1 resistor is trimmed 24
upwards or downwards until the difference between V1 and V2 is
within the window (hysteresis) of the comparator.
[0027] FIG. 7 is a schematic of resistor trim circuit according to
an embodiment of the invention. FIG. 7 shows one embodiment of a
possible resistor trim method but many others are known to those
skilled in the art. In this example, the feedback resistor consists
of two primary resistors, RA and RB, and a series of trim
resistors, R1 to RN. The trim resistors, R1 to RN, are much smaller
than the primary feedback resistors. The FB node may be connected
to any tap point along the R1, RN string of resistors by means of a
low-voltage CMOS switch. By changing the tap-point on the resistor
string, the resistor ratio is trimmed.
[0028] Additionally, in order to improve the power consumption of
the amplifier, it is desirable to have multiple high-voltage power
supply rails to choose from. In order to accommodate this
requirement, the operational amplifier is sub regulated such that
when power supply for the operational amplifier is changed, the
output of the amplifier is not disturbed. FIG. 4 is an
implementation of this technique. It shows a channel multiplexed to
a high-voltage rail with a sub-regulator between the between the
high-voltage rail and the internal rail of the amplifier according
to an embodiment of the invention. A digital or analog command
device sets the voltage channel 26 in conformance with the desired
output voltage. A controller acts to: i) group channels which are
commanded to an output voltage together such that all the rails
with similar voltage outputs or lower output voltages but above any
other rail output voltage may be run off a single rail set just
above the voltage of the highest commanded voltage in the group
where the number of groupings equals the number of possible rails;
ii) calculates the required voltage on each rail and dynamically
establishes the output voltage of each rail.
[0029] Although the movement of the high voltage rails may be
easily accomplished by changing the feedback of the boost converter
and or charge pumps creating the rails, the transient involved with
this movement may couple through the voltage output or current
mirror outputs of the devices setting the output rail voltages. To
decouple these movements from those outputs a sub regulator may be
used as in FIG. 4 where the high voltage rails are set by a
follower. In this case an n-channel device is used as the follower
which results in a high impedance to any ac signals introduced on
its drain by the movement of the supply rail voltage
magnitudes.
[0030] Semiconductor devices such as integrated MOSFETs tend to
grow substantially in size according to the voltage they have to
block. High voltage MOSFETs also tend to have poor matching
characteristics. It is therefore a common technique in high voltage
processes to create isolated tubs in which lower voltage devices
may float relative to other parts of the circuit. In other words,
the components form low voltage "slices" which may operate in a
small region or slice within a few volts of a voltage supply input
but would be damaged if more than an allowed voltage were placed
across the devices. Such slices may be accomplished through
junction or dielectric isolation and are well known to those
skilled in the art. These slices may be moved around relative to
one another. Although multiple rails may be used to operate
multiple channels the voltage must be higher than the highest
voltage commanded output in the group, and the voltage on other
slices in the group must still be sub-regulated from that supply
rail so as not to damage slices further away from the rail. This is
another reason, in addition to the noise decoupling during rail
movements, to include a sub-regulator.
[0031] In inventive embodiments multiple rails are generated on the
same chip so as to reduce the EMI loops on a standard printed
circuit board (PCB). This is best, although can be accomplished
without, using a dielectrically isolated process which is capable
of isolating the noise of the switching power supply from other
circuits on the same monolithic die. The circuitry includes a
controller, feedback means (which can be calibrated using the same
external precision reference as the other channels), and a
combination of boost and charge pump stages depending upon the
number of rails desired. FIG. 5 is a schematic of a complete
multichannel MEMS driver solution including internally generated
multiple supply rails according to an embodiment of the invention.
FIG. 6 is a schematic of a channel connected to one of multiple
supply rails according to an embodiment of the invention. FIG. 7
shows a possible means for resistor divider adjustment. FIG. 8 is a
schematic of a boost integrated circuit configuration with charge
pumps according to an embodiment of the invention.
[0032] There are multiple ways to implement embodiments of the
invention including differing loop configurations, feedback
combinations or coupling techniques that are known to those skilled
in the art and which might be used as an alternative to elements of
the above methods and circuits without altering the innovation
taught herein.
[0033] There are multiple ways to implement the calibration
sequence including continuously calibrating one channel,
periodically calibrating one channel, rotating through and
calibrating each channel in sequence continuously, calibrating each
channel when its output value is changed, or any other method
deemed optimal.
[0034] There are multiple ways of implementing the high-voltage
operational amplifier. It could be implemented with a low-voltage
input stage followed by a folded cascode stage to a high-voltage
output stage. Alternatively, it could be implemented with a
low-voltage input operational amplifier driving a transconductor
which in turn drives a high-voltage current mirror which is then
used to set the current through the high-side feedback resistor and
can be mirrored to outputs coupled to other dividers. There are
many implementations of high-voltage operational amplifiers known
to those skilled in the art.
[0035] As mentioned, it would be desirable to save power by
generating multiple high voltage rails such that groups of outputs
of lower expected output voltage may be coupled to those rails to
save power, rather than drawing all of their current from one high
voltage rail which might be much higher than required, for all
outputs. Generating multiple high voltage rails usually requires
multiple feedback loops and switches, some using the output of one
of the previous stages as the input to the next stage. Instead,
quadratic and doubling techniques might be used. As shown in FIG. 8
a single switch may be used to create multiple rails. One of the
rails may be chosen for regulation and a wider variation in the
other rails accepted. By further incorporating the feedback, driver
and switch components monolithically, the overall system size may
be reduced substantially compared to using external discrete
components. Although a single boost converter stage and multiple
doubler (charge pump) stages are shown, the replacement of any of
D2/C2 or D4/C4 with an inductor in series with a diode, where the
drain of the switch were connected to the node connecting the
inductor and diode would allow greater conversion ratios for the
subsequent stages. In this figure, L1, M, C1, and D form a
traditional boost converter to create the voltage, V1. The
capacitor, C2, and diodes D2 and D3 create a charge pump stage.
Assuming the diode drops to be negligible with respect to V1, V2,
and V3 simplifies the analysis of the circuit. The drain of M
switches roughly between ground and V1. The capacitor, C2, pushes
this voltage onto the cathode of D2 such that the cathode of D2
switches between roughly V1 plus V1. The voltage V2 is therefore
roughly double V1. The C4 capacitor and the D4 and D4 capacitors
act similarly such that V3 is equal roughly to V1 plus V2 or three
times the V1 voltage. FIG. 8 shows one embodiment of a boost
converter generating three high-voltage rails, however, this
topology could be used to generate any number of such rails.
[0036] Switching circuits such as DC/DC converters (switching power
supplies) or charge pumps tend to cause noise which couples through
the substrate if included monolithically on an integrated circuit.
This would be particularly problematic in the proposed circuit
where high impedance on chip resistor dividers would be susceptible
to noise coupled through the substrate. To reduce the probability
of such noise coupling, a dielectrically isolated process may be
used and isolated tubs created such that the switching circuits and
the precision analog circuitry are isolated from each other.
[0037] The foregoing description is illustrative of particular
embodiments of the invention, but is not meant to be a limitation
upon the practice thereof. The following claims, including all
equivalents thereof, are intended to define the scope of the
invention.
* * * * *