isl24212 Intersil Corporation, isl24212 Datasheet - Page 9

• Manufacturer Part Number: isl24212
• Description: Programmable Vcom Calibrator With Eeprom And Output Buffer
• Manufacturer: Intersil Corporation

CE Pin
To change the counter controlling the output voltage, the CE
(Counter Enable) pin must be pulled high (V
is pulled low, the counter value is loaded from EEPROM, which
takes 10ms (during which the inputs should remain constant).
The CE pin has an internal pull-down to keep it at a logic low
when not being driven. CE should be pulled low before powering
the device down to ensure that any glitches or transients during
power-down will not cause unwanted EEPROM overwriting.
The CE pin has a Schmitt trigger on the input to prevent false
triggering during slow transitions of the CE pin. The CE pin
transition time should be 10µs or less.
Programming the EEPROM
To program the non-volatile EEPROM, pull the CTL pin above 4.9V
for more than 200µs. The level and timing is shown in Figure 9. It
then takes a maximum of 100ms after CTL crosses 4.9V for the
programming to be completed inside the device.
When the part is programmed, the data in the counter register is
written into the EEPROM. This value will be loaded from the
EEPROM during subsequent power-ups as well as when the CE
pin is pulled low. The ISL24212 is factory-programmed to
mid-scale. As with asserting CE, the first pulse after a program
operation is ignored. The EEPROM contents can be written and
verified using the following steps:
4.9V
CTL VOLTAGE
PROGRAM
CLOSE TO
EEPROM
FIGURE 9. EEPROM PROGRAMMING
1kΩ
SW1
AV
DD
t
>200µs
PROG
SW2
SW3
1kΩ
1kΩ
9
V
DD
100ms
DOWN
COMPLETE
UP
OPERATION
EEPROM
PROGRAM
ENABLE
ADJUST /
DISABLE
DD
). When the CE pin
0.01µF
0.01µF
V
DD
FIGURE 10. TYPICAL APPLICATION CIRCUIT
SW4
TIME
0.1µF
ISL24212
CTL
CE
V
DD
GND
V
DD
ISL24212
The CTL pin should be left floating after programming. The
voltage at the CTL pin will be internally biased to V
that no additional pulses will be seen by the Up/Down counter. To
prevent further changes, ground the CE pin.
Typical Application Circuit
Shown below in Figure 10 is a typical circuit that can be used to
program the ISL24212 via the up/down counter interface. Three
momentary push-button switches are required. SW1 connected
between CTL and AV
programming the EEPROM, SW2 connected to V
and SW3 connected to GND to pull CTL to down. All the switches
should have 1k
For adjustment and programming to occur, the CE pin has to be
set to V
switch (SW4) connected between V
Note that pressing the UP button increments the counter, but
results in V
button decrements the counter, and results in V
increasing.
1. Power-up the ISL24212. The EEPROM value will be loaded.
2. Set the CE pin to V
3. Change the V
4. Pull the CTL pin to 4.9V or higher for at least 200µs. The
5. Change the V
6. Set the CE pin to 0V. The stored output value will be loaded
7. Verify that the output value is the same value programmed in
AV
value, noting that first pulse will be ignored.
counter value will be written to EEPROM after 100ms.
noting that first pulse after programming will be ignored.
from EEPROM after 10ms.
Step 4.
DD
AV
RSET
DD
DD
. This can be achieved by a single-pull double-throw
COM_OUT
0.1µF
SET
VCOM_OUT
DVR_OUT
Ω
OUT
OUT
current-limiting resistors in series.
DD
IN
decreasing. Similarly, pressing the DOWN
value (using the CTL pin) to a different value,
voltage using the CTL pin to the desired
N
DD
allows the user to bring CTL above V
.
R2
R1
AV
DD
DD
V
COM
and GND.
to LCD Panel
DD
COM_OUT
DD
to pull CTL up,
/2 to ensure
March 15, 2011
FN7590.0
DD
for