MP1531 Datasheet, PDF (7/12 Pages) Monolithic Power Systems – Low Power, Triple Output Step-Up Plus Charge Pump for TFT Bias

MP1531 – LOW POWER, TRIPLE OUTPUT STEP-UP PLUS CHARGE PUMP FOR TFT BIAS
V_GH
OUTPUT
VOLTAGES
V_IN
0V
V_MAIN
V_IN
IN
0V
V_EN-HIGH
EN
0V
1.25V
CT
0V
V_IN
RDY
0V
V_GL
POWER ON RESET START 1
START 2
START 3
TIME
Figure 2—Start-Up Timing Diagram
APPLICATION INFORMATION
Setting the Output Voltages
Set the output voltage on each output by
selecting the resistive voltage divider ratio. The
voltage divider drops the output voltage to the
feedback threshold voltage. Use 10kΩ to 50kΩ
for the low-side resistor of the voltage divider.
For the step-up converter, determine the
high-side resistor R1 by the equation:
R1 = ^{VMAIN − VFB1}
⎜⎜⎝⎛
V_FB1
R2
⎟⎟⎠⎞
Where V_MAIN is the output voltage of the step-up
converter.
For the positive charge-pump, determine the
high-side resistor R9 by the equation:
R9 = ^{VGH − VFB3}
⎜⎜⎝⎛
V_FB3
R8
⎟⎟⎠⎞
For the negative charge-pump, determine the
high-side resistor R7 by the equation:
R7 = ^−VGL
⎜⎜⎝⎛
V_REF
R5
⎟⎟⎠⎞
MP1531 Rev. 1.2
www.MonolithicPower.com
7
5/22/2006
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