ISL45042A Intersil Corporation, ISL45042A Datasheet - Page 5

• Manufacturer Part Number: ISL45042A
• Description: LCD Module Calibrator
• Manufacturer: Intersil Corporation

When the part is programmed, the counter setting is loaded
into the non-volatile memory. This value will be loaded from
the nonvolatile memory during initial power-up or when the
CE pin is pulled low.
Once the programming is completed it is recommended that
the user float the CLT pin. The CTL pin is internally tied to a
resistor network connected to ground. If left floating, the
voltage at the CTL pin will equal V
conditions, no additional pulses will be seen by the Up/Down
counter via the CTL pin. To prevent further programming
ground the CE pin.
CTL should have a noise filter to reduce bouncing or noise
on the input that could cause unwanted counting when the
CE pin is high. The board should have an additional ESD
protection circuit, with a series 1kΩ resistor and a shunt
0.01µF capacitor connected on the CTL pin. (See Figure 3)
4.9V
FIGURE 3. EXTERNAL ESD PROTECTION ON CTL PIN
CTL VOLTAGE
FIGURE 4. EXAMPLE OF THE REPLACEMENT FOR THE MECHANICAL POTENTIOMETER CIRCUIT USING THE ISL45042A
R
R
R
b
c
a
AVDD
FIGURE 2. EEPROM PROGRAMMING
0.01µF
1kΩ
-
+
CTL
>200µs
CTL
PT
ISL45042A
5
DD
/2. Under these
VCOM
R
R
R
1
2
SET
= Rb + Rc
= Ra
= (Ra(Rb + Rc)) / 20Rb
TIME
ISL45042A
To avoid unintentional adjustment, the ISL45042A
guarantees to reject CTL pulses shorter than 20µs.
During Initial Power-up (only), to avoid the possibility of a
false pulse (since the internal comparators come up in an
unknown state) the very first CTL pulse is ignored. See
Figure 6 for the timing information..
CE Pin
To adjust the output voltage, the CE pin must be pulled high
(VDD). The CE pin has an internal pull-down resistor to
prevent unwanted reprogramming of the EEPROM. The
impedance of this resistor is 400kΩ to 500kΩ (R
Figure 5).
The CE pin has a Schmitt trigger on the input to prevent
false triggering during slow transitions of the CE pin.
Transitions of the CE pin are recommended to be less than
10µs.
Replacing Existing Mechanical Potentiometer
Circuits
Figure 4 shows the common adjustment mechanical circuits
and equivalent replacement with the ISL45042A.
Expected Output Voltage
The ISL45042A provides an output sink current which lowers
the voltage on the external voltage divider (VCOM output
voltage). EQ. 1 and EQ. 2 can be used to calculate the
output current (IOUT) and output voltage (VOUT) values.
VOUT
NOTE: Where setting is an integer between 1 and 128.
IOUT
=
=
AVDD
Setting
-------------------- - X
⎛
⎝
--------------------- -
R1
128
SET
ISL45042A
R2
+
R
R2
SET
⎞ AVDD 1 Setting
⎠
---------------------------- -
20 RSET
OUT
AVDD
(
⎛
⎝
)
–
AVDD
-------------------- - X
128
R
R
1
2
---------------------------- -
20 RSET
(
-
+
R1
)
⎞
⎠
INTERNAL
October 13, 2006
VCOM
FN6158.2
(EQ. 1)
(EQ. 2)