5

FN6072.7

August 29, 2007

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 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

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 7 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 400k

Figure 6).

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.

Expected Output Voltage

The ISL45042 provides an output sink current, which lowers

voltage). Equation 1 and Equation 2 can be used to calculate

NOTE: Where setting is an integer between 1 and 128.

CTL VOLTAGE

TIME

4.9V

FIGURE 2. EEPROM PROGRAMMING

>200µs

FIGURE 3. EXTERNAL ESD PROTECTION ON CTL PIN

ISL45042

CTL

0.01µF

1k

Ω

I

OUT

Setting

128

--------------------- x

AV

DD

20 R

SET

()

---------------------------

=

V

OUT

R

2

R

1

R

2

+

---------------------

⎝⎠

⎜⎟

⎛⎞

AV

Setting

128

--------------------- x

R

1

20 R

SET

()

---------------------------

–

⎝⎠

⎜⎟

⎛⎞

=

(EQ. 1)

(EQ. 2)

-

+

-

+

ISL45042

SET

OUT

AVDD

AVDD

VCOM

VCOM

AVDD

FIGURE 4. EXAMPLE OF THE REPLACEMENT FOR THE MECHANICAL POTENTIOMETER CIRCUIT USING THE ISL45042

ISL45042