Electronic Components Datasheet Search |
|
ISL24202IRTZ-EVALZ Datasheet(PDF) 6 Page - Intersil Corporation |
|
ISL24202IRTZ-EVALZ Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 12 page ISL24202 6 FN7587.0 March 15, 2011 Application Information LCD panels have a VCOM (common voltage) that must be precisely set to minimize flicker. Figure 3 shows a typical VCOM adjustment circuit using a mechanical potentiometer, and the equivalent circuit replacement using the ISL24202. Having a digital counter interface enables automatic, digital flicker minimization during production test and alignment. After programming, the counter interface is not needed again - the ISL24202 automatically powers up with the correct VCOM voltage programmed previously. The ISL24202 uses a digitally controllable potentiometer (DCP), with 256 steps of resolution (Figure 4) to change the current drawn at the OUT pin, which then changes the voltage created by the R1 - R2 resistor divider (Figure 5). The OUT voltage can then be buffered by an external amplifier (A2) to generate a buffered output voltage (VCOM) capable of driving the VCOM input of an LCD panel. The amount of current sunk is controlled by the setting of the DCP, which is recalled at power-up from the ISL24202’s internal EEPROM. The EEPROM is typically programmed during panel manufacture. As noted in the “Electrical Specifications” section on page 4, the ISL24202 requires a minimum AVDD voltage of 10.8V for EEPROM programming, but will work in normal operation down to 4.5V after the EEPROM has been programmed, with no additional EEPROM writing. 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 OUT current sink. The combination of amplifier A1, transistor Q1, and resistor RSET forms a voltage-controlled current source, with the voltage determined by the DCP setting. The external RSET resistor sets the full-scale (maximum) sink current that can be pulled from the OUT node. The relationship between IOUT and Register Value is shown in Equation 2. The maximum value of IOUT can be calculated by substituting the maximum register value of 255 into Equation 2, resulting in Equation 3: Equation 2 can also be used to calculate the unit sink current step size per Register Code, resulting in Equation 4: FIGURE 3. MECHANICAL ADJUSTMENT REPLACEMENT SET ISL24202 R1 R2 AVDD AVDD VCOM IOUT VDD RSET RA RC AVDD VCOM RB R1 = RA R2 = RB+RC RSET = RARB + RARC 20RB OUT A2 VDCP RegisterValue 1 + 256 --------------------------------------------------- ⎝⎠ ⎛⎞ AVDD 20 -------------- ⎝⎠ ⎛⎞ = (EQ. 1) FIGURE 4. SIMPLIFIED SCHEMATIC OF DCP AVDD 19R R 0 1 2 255 254 253 252 251 REGISTER VALUE AVDD 20 VDCP FIGURE 5. CURRENT SINK CIRCUIT AVDD RSET VDCP SET OUT AVDD IOUT R1 R2 VSAT Q1 A1 VOUT VSET = VDCP = IOUT * RSET IOUT IOUT VDCP RSET ------------- RegisterValue 1 + 256 --------------------------------------------------- ⎝⎠ ⎛⎞ AVDD 20 -------------- ⎝⎠ ⎛⎞ 1 RSET ------------- ⎝⎠ ⎛⎞ == (EQ. 2) IOUT MAX () AVDD 20RSET -------------------- = (EQ. 3) ISTEP AVDD 256 () 20 () R SET () ---------------------------------------------- = (EQ. 4) |
Similar Part No. - ISL24202IRTZ-EVALZ |
|
Similar Description - ISL24202IRTZ-EVALZ |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |