High-Efficiency, Quad Output, Main Power-

Supply Controllers for Notebook Computers

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13

PIN

NAME

FUNCTION

1

ONA

Auxiliary LDO Enable Input. When ONA is pulled low, OUTA is high impedance and the secondary

feedback control is disabled. When ONA is driven high, the controller enables the auxiliary LDO.

2

DRVA

Auxiliary LDO Transistor Base Driver. Connect DRVA to the base of a pnp power transistor. Add a

680

Ω pullup resistor between the base and emitter.

3

ILIM

Peak Current-Limit Threshold Adjustment. The current-limit threshold defaults to 50mV if ILIM is pulled

up to LDO5. In adjustable mode, the current-limit threshold across CSH_ and CSL_ is precisely 1/10

the voltage seen at ILIM over a 0.5V to 2.0V range. The logic threshold for switchover to the 50mV

4

SHDN

5

ON3

3.3V SMPS Enable Input. Driving ON3 high enables the 3.3V SMPS, while pulling ON3 low disables

the 3.3V SMPS. If ON3 is connected to REF, the 3.3V SMPS starts after the 5V SMPS reaches

regulation (delayed start). Drive ON3 below the clear fault level to reset the fault latch.

6

ON5

5V SMPS Enable Input. Driving ON5 high enables the 5V SMPS, while pulling ON5 low disables the

5V SMPS. If ON5 is connected to REF, the 5V SMPS starts after the 3.3V SMPS reaches regulation

(delayed start). Drive ON5 below the clear fault level to reset the fault latch.

7

REF

2.0V Reference Voltage Output. Bypass REF to analog ground with a 0.1µF or greater ceramic

capacitor. The reference sources up to 50µA for external loads. Loading REF degrades output-

voltage accuracy according to the REF load-regulation error. The reference shuts down when the

system pulls SHDN low.

8

GND

Analog Ground. Connect the exposed backside pad to GND.

9

FSEL

Frequency Select Input. This three-level logic input sets the controllers’ switching frequency. Connect

to LDO5, REF, or GND to select the following typical switching frequencies:

LDO5 = 500kHz, REF = 300kHz, GND = 200kHz.

10

SKIP

Pulse-Skipping Control Input. Connect to LDO5 for low-noise, forced-PWM operation. Connect to REF

for automatic, low-noise, pulse-skipping operation at light loads. Connect to GND for automatic, high-

efficiency, pulse-skipping operation at light loads.

11

FB5

Feedback Input for the 5V SMPS. Connect to LDO5 for the preset 5V output. In adjustable mode, FB5

regulates to 2V.

12

CSH5

Positive Current-Sense Input for the 5V SMPS. Connect to the positive terminal of the current-sense

element. Figure 7 describes two different current-sensing options—using accurate sense resistors or

lossless inductor DCR sensing.

13

CSL5

Output-Sense and Negative Current-Sense Input for the 5V SMPS. When using the internal preset 5V

feedback-divider (FB5 = LDO5), the controller uses CSL5 to sense the output voltage. Connect to the

negative terminal of the current-sense element. CSL5 also serves as the bootstrap input for LDO5.

14

PGOOD5

Open-Drain, Power-Good Output for the 5V SMPS. PGOOD5 is pulled low if CSL5 drops more than

10% (typ) below the normal regulation point. PGOOD5 is held low during soft-start and shutdown.

PGOOD5 becomes high impedance when CSL5 is in regulation.

Pin Description