ISL24211

6

FN7585.0

February 23, 2011

Application Information

circuit using a mechanical potentiometer, and the equivalent

interface enables automatic, digital flicker minimization during

interface has no further use therefore, the ISL24211 automatically

The ISL24211 uses a digitally controllable potentiometer (DCP),

with 256 steps of resolution (see Figure 4) to change the current

drawn at the DVR_OUT pin, which then changes the voltage

DVR_OUT voltage is then buffered by A2 to generate a buffered

controlled by the setting of the DCP, which is recalled at power-up

from the ISL24211’s internal EEPROM. The EEPROM is typically

programmed during panel manufacture. As noted in the

Electrical Specifications on page 4, the ISL24211 requires a

will work in normal operation (with no EEPROM programming)

down to 4.5V.

DCP (Digitally Controllable Potentiometer)

The DCP controls the voltage that ultimately controls the SET

current. Figure 4 shows the relationship between the register

value and the DCP’s tap position. Note that a register value of 0

selects the first step of the resistor string. The output voltage of

the DCP is given in Equation 1:

Output Current Sink

Figure 5 shows the schematic of the DVR_OUT current sink. The

forms a voltage-controlled current source, with the voltage

determined by the DCP setting.

that can be pulled from the DVR_OUT node. The relationship

FIGURE 3. MECHANICAL ADJUSTMENT REPLACEMENT

DVR_OUT

SET

ISL24211

VCOM_OUT

RegisterValue 1

+

256

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

⎝⎠

20

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

⎝⎠

⎛⎞

=

(EQ. 1)

FIGURE 4. SIMPLIFIED SCHEMATIC OF DCP

19R

R

0

1

2

255

254

253

252

251

REGISTER

VALUE

20

FIGURE 5. CURRENT SINK CIRCUIT

SET

DVR_OUT

Q1

A1

VCOM_OUT

GND

A2

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

RegisterValue 1

+

256

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

⎝⎠

20

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

⎝⎠

⎛⎞

1

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

⎝⎠

⎛⎞

==

(EQ. 2)