ADP3020

–4–

REV. 0

PIN FUNCTION DESCRIPTIONS

Pin No.

Mnemonic

Function

1

CS5

Current Sense Input for top N-Channel MOSFET of the 5 V Buck Converter. Connect to the drain of

the top N-channel MOSFET.

2

FB5

Feedback Input for the 5 V Buck Converter. Connect to the output sense point in fixed output mode.

Connect to an external resistor divider in adjustable output mode.

3

EAN5

Inverting Input of the Error Amplifier of the 5 V Buck Converter. Use for external loop compensation

only in fixed output mode. In adjustable output mode, connect to an external resistor divider.

4

EAO5

Error Amplifier Output for the 5 V Buck Converter.

5

ADJ/FX5

TTL Logic Input. When ADJ/FX5 = 0 V, fixed output mode, connect FB5 to the output sense point.

When ADJ/FX5 = 5 V, adjustable output mode, connect FB5 to the external resistor divider.

6

SS5

Soft Start for the 5 V Buck Converter. Also used as an ON/OFF Pin.

7

CLSET5

Current Limit Setting. A resistor can be connected from AGND to CLSET5. A minimum current

limit is obtained by leaving it unconnected. A max current limit is obtained by connecting it to AGND.

8

REF

1.2 V Bandgap Reference. Bypass it with a capacitor (1 nF typical) to AGND. REF cannot be used

directly with an external load.

9

AGND

Analog Signal Ground.

10

CLSET3

Current Limit Setting. A resistor can be connected from AGND to CLSET3. A minimum current

limit is obtained by leaving it unconnected. A max current limit is obtained by connecting it to AGND.

11

MODE

TTL Logic Input. MODE = 5 V, always in constant frequency PWM mode; MODE = 0 V, PWM

mode at moderate and heavy loads, and Power Saving (PSV) Mode at light load.

12

SYNC

external source through the SYNC Pin.

13

SS3

Soft Start for the 3.3 V Buck Converter. Also used as an ON/OFF Pin

14

ADJ/FX3

TTL Logic Input. When ADJ/FX3 = 0 V, fixed output mode, connect FB3 to the output sense point.

When ADJ/FX3 = 5 V, adjustable output mode, connect FB3 to external resistor divider.

15

EAO3

Error Amplifier Output for the 3.3 V Buck Converter.

16

EAN3

Error Amplifier Inverting Input of the 3.3 V Buck Converter. Use for external loop compensation only in

fixed output mode. In adjustable output mode, connect to an external resistor divider.

17

FB3

Feedback Input for the 3.3 V Buck Converter. Connect to output sense point in fixed output mode.

Connect to an external resistor divider in adjustable output mode.

18

CS3

Current Sense Input for Top N-Channel MOSFET of the 3.3 V Buck Converter. It should be con-

nected to the drain of the N-channel MOSFET.

19

PFI

The (–) Input of a comparator that can be used as a power fail detector. The positive input is connected

to the 1.20 V reference. There is a 24 mV hysteresis for this comparator.

20

PFO

Open Drain Output. This pin will sink current when the PFI pin is lower than 1.20 V. Otherwise, PFO

is floating.

21

PWRGD

Power Good Output. PWRGD goes low with no delay, whenever the 5 V output drops 8% below its

nominal value. When the 5 V output is within –4% of its nominal value, PWRGD will be released after a

time delay determined by the timing capacitor on the CPOR pin.

22

CPOR

Connect a capacitor between CPOR and AGND to set the delay time for the PWRGD pin. A 2.5

µA

pull-up current is used to charge the capacitor. A manual reset (MR) function can also be implemented

by grounding this pin.

23

SD2

Shutdown input for the Linear Regulator Controller.

24

FB2

Feedback for the Linear Regulator Controller.

25

DRV2

Open Collector Output for the Linear Regulator Controller.

26

BST3

Boost Capacitor Connection for High Side Gate Driver of the 3.3 V Buck Converter.

27

DRVH3

High Side Gate Driver for 3.3 V Buck Converter.

28

SW3

Switching Node (Inductor) Connection of the 3.3 V Buck Converter.

29

DRVL3

Low Side Gate Driver of 3.3 V Buck Converter.

30

VIN

Main Supply Input (4.5 V to 25 V).