ISL24202_14 Datasheet, PDF (9/12 Pages) Intersil Corporation – Programmable VCOM Calibrator with EEPROM

ISL24202
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.
CTL VOLTAGE
4.9V
>200µs
EEPROM
OPERATION
COMPLETE
100ms
t_PROG
TIME
FIGURE 9. EEPROM PROGRAMMING
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 ISL24202 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:
1. Power-up the ISL24202. The EEPROM value will be loaded.
2. Set the CE pin to V_DD.
3. Change the V_OUT voltage using the CTL pin to the desired
value, noting that first pulse will be ignored.
4. Pull the CTL pin to 4.9V or higher for at least 200µs. The
counter value will be written to EEPROM after 100ms.
5. Change the V_OUT value (using the CTL pin) to a different value,
noting that first pulse after programming will be ignored.
6. Set the CE pin to 0V. The stored output value will be loaded
from EEPROM after 10ms.
7. Verify that the output value is the same value programmed in
Step 4.
The CTL pin should be left floating after programming. The
voltage at the CTL pin will be internally biased to V_DD/2 to ensure
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 ISL24202 via the up/down counter interface. Three
momentary push-button switches are required. SW1 connected
between CTL and AV_DD allows the user to bring CTL above V_DD for
programming the EEPROM, SW2 connected to V_DD to pull CTL up,
and SW3 connected to GND to pull CTL to down. All the switches
should have 1kΩ current-limiting resistors in series.
For adjustment and programming to occur, the CE pin has to be
set to V_DD. This can be achieved by a single-pull double-throw
switch (SW4) connected between V_DD and GND.
Note that pressing the UP button increments the counter, but
results in V_{COM_OUT} decreasing. Similarly, pressing the DOWN
button decrements the counter, and results in V_{COM_OUT}
increasing.
AV_DD
1kΩ
CLOSE TO
PROGRAM
EEPROM
SW1
V_DD
V_DD
ENABLE
ADJUST /
PROGRAM
SW4
1kΩ
SW2
DISABLE
UP
DOWN
SW3
0.01µF
1kΩ
V_DD
0.1µF
AV_DD
0.1µF
V_DD AV_DD
CE
ISL24202
OUT
CTL
GND
SET
R_SET
AV_DD
R₁
R₂
EL5411T
V_COM to LCD Panel
FIGURE 10. TYPICAL APPLICATION CIRCUIT
9
FN7587.0
March 15, 2011