MP1531 – LOW POWER, TRIPLE OUTPUT STEP-UP PLUS CHARGE PUMP FOR TFT BIAS
PIN FUNCTIONS
QFN16 TSSOP16
Pin #
Pin #
Name Description
1
15
SW Step-Up Converter Power Switch Node. Connect an inductor between the input source
and SW, and connect a rectifier from SW to the main output to complete the step-up
converter. SW is the drain of the internal 250mΩ N-Channel MOSFET switch.
2
16
CT
Timing Capacitor for Soft-Start and Power-On Sequencing. A capacitor from CT to
GND controls the soft-start and sequencing turn-on delay periods. See
Power-On
Sequencing and Start-Up Timing Diagram.
3
1
RDY
Regulators Not Ready. This pin is an open drain output, and an external 100kΩ
pull-up resistor is required for proper operation. During startup
RDY
will be high
impedance. Once the turn-on sequence is complete, this pin will be pulled low if all
FB voltages exceed 80% of their specified thresholds. After all regulators are
turned-on, a fault in any regulator that causes the respective FB voltage to fall
below 80% of its threshold will cause
RDY
to go high after approximately 15µs. If
the fault persists for more than approximately 6ms (for C4 = 10nF), the entire chip
will shut down. See Fault Sensing and Timer.
FB1 Step-Up Converter Feedback Input. FB1 is the inverting input of the internal error
amplifier. Connect a resistive voltage divider from the output of the step-up
converter to FB1 to set the step-up converter output voltage.
COMP Step-Up Converter Compensation Node. COMP is the output of the error amplifier. Connect
a series RC network to compensate the regulation control loop of the step-up converter.
IN
Internal Power Input. IN supplies the power to the MP1531. Bypass IN to PGND
with a 10µF or greater capacitor.
GND Signal Ground.
REF Reference Output. REF is the 1.25V reference voltage output. Bypass REF to GND
with a 0.1µF or greater capacitor. Connect REF to the low-side resistor of the
negative linear regulator feedback string.
FB2 Negative Linear Regulator Feedback Input. Connect the FB2 feedback resistor
string between GL and REF to set the negative linear regulator output voltage. FB2
regulation threshold is GND.
FB3 Positive Linear Regulator Feedback Input. Connect the FB3 feedback resistor string
between GH and GND to set the positive linear regulator output voltage. FB3
regulation threshold is 1.25V.
EN On/Off Control Input. Drive EN high to turn on the MP1531, drive EN low to turn it
off. For automatic startup, connect EN to IN. Once the MP1531 is turned on, it
sequences the outputs on (See
Power-On Sequencing).
When turned off, all
outputs are immediately disabled.
GL Negative Linear Regulator Output. GL is the output of the negative linear regulator.
GL can supply up to 10mA to the load. Bypass GL to GND with a 1µF or greater,
low-ESR, ceramic capacitor.
IN2 Negative Linear Regulator Input. IN2 is the input of the negative linear regulator. Drive
IN2 with an inverting charge pump powered from SW. IN2 can go as low as –20V. For
QFN package IN2 connects to exposed pad.
GH Positive Linear Regulator Output. GH is the output of the positive linear regulator.
GH can supply as much as 10mA to the load. Bypass GH to GND with a 1µF or
greater, low-ESR, ceramic capacitor.
IN3 Positive Linear Regulator Input. IN3 is the input to the positive linear regulator.
Drive IN3 with a doubling, tripling, or quadrupling charge pump from SW. IN3
voltage can go as high as 38V.
PGND Power Ground. PGND is the source of the internal 250mΩ N-Channel MOSFET
switch. Connect PGND to GND as close to the MP1531 as possible.
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© 2006 MPS. All Rights Reserved.
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16
14
MP1531 Rev. 1.2
5/22/2006
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MPS [ MONOLITHIC POWER SYSTEMS ]
