5

FN6072.9

April 13, 2011

Application Information

panel is shown in Figure 1. The ISL45042 has a 128-step

sink current resolution. The output is connected to an

voltage as you increase the ISL45042 sink current.

CTL Pin

programming of the non-volatile memory are provided

through a single pin called CTL when the CE pin is high.

or maximum value is reached on the 128 steps, the device

will not overflow or underflow beyond that minimum or

maximum value.

Programming of the non-volatile memory occurs when the

CTL pin exceeds 4.9V. The CTL signal needs to remain

above 4.9V for more than 200µs. The level and timing

needed to program the non-volatile memory is given in

Figure 2. It then takes a maximum of 100ms for the

programming to be completed inside the device.

When the part is programmed, the counter setting is loaded

into the non-volatile memory. This value will be loaded from

the non-volatile 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 CTL pin. The CTL pin is internally tied to a

resistor network connected to ground. If left floating, the

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 1k

Ω resistor and a shunt

0.01µF capacitor connected on the CTL pin, (see Figure 3).

To avoid unintentional adjustment, the ISL45042 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 8 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. To

minimize current consumption, the impedance of this resistor

is high: 400k

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 ISL45042.

FIGURE 1. VCOM ADJUSTMENT IN AN LCD PANEL

ISL45042

SET

OUT

AVDD

AVDD

VCOM

SINGLE PIXEL

CTL

CE

IN LCD PANEL

+

-

COLUMN

DRIVER

CTL VOLTAGE

TIME

4.9V

FIGURE 2. EEPROM PROGRAMMING

>200µs

ISL45042