MP1531 – LOW POWER, TRIPLE OUTPUT STEP-UP PLUS CHARGE PUMP FOR TFT BIAS

MP1531 Rev. 1.2

www.MonolithicPower.com

7

5/22/2006

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© 2006 MPS. All Rights Reserved.

OUTPUT

VOLTAGES

0V

0V

IN

0V

0V

1.25V

POWER ON RESET

START 1

START 2

TIME

START 3

CT

EN

0V

RDY

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:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

=

2

R

V

V

V

1

R

1

FB

1

FB

MAIN

converter.

For the positive charge-pump, determine the

high-side resistor R9 by the equation:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

=

8

R

V

V

V

9

R

3

FB

3

FB

GH

For the negative charge-pump, determine the

high-side resistor R7 by the equation:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

=

5

R

V

V

7

R

REF

GL