ADP1974

Data Sheet

Rev. 0 | Page 10 of 19

THEORY OF OPERATION

FREQ

SYNC

VIN

VIN

SYNC

DETECT

5µA

VREG

SS DISCHARGE

COMP

SS

FAULT

GND

EN

ADP1974

VREG

AD8450

AD8450

DMAX

SCFG

TSD

VREG

UVLO

BAND GAP

MODE

VREG

DH

DL

DRIVE

LOGIC

OSCILLATOR

CONFIG

DETECT

CL

VREG

EXTERNAL

DRIVER

5V

15V

24V

VOUT

500mV

450mV

300mV

MODE

SELECT

4V

20µA

20µA

MODE

SELECT

PGND

AGND

1MΩ

1MΩ

1MΩ

1kΩ

20kΩ

4.7µF

1µF

L

M1

M2

VREG = 5V

8.5MΩ

VREG

VREG

VREG

10µA

DT

1.64pF

VREG

Figure 20. Internal Block Diagram

The ADP1974 is a constant frequency, voltage mode, synchronous,

PWM controller for bidirectional dc-to-dc applications. The

ADP1974 is designed to be used with an external, high voltage

FET half bridge driver, such as the ADuM7223, and an external

error amplifier AFE device, such as the AD8450/AD8451, to

implement a battery testing, charging, and discharging system.

The ADP1974 has a high input voltage range, multiple externally

programmed control pins, and integrated safety features. In

buck mode, the device charges a battery and delivers energy

from the input power source to the output. In boost mode, the

device discharges a battery and delivers energy from the battery

to the input. In both modes, the ADP1974 operates as a

synchronous controller for maximum efficiency.

SUPPLY PINS

The ADP1974 has two voltage supply pins, VIN and VREG.

The VIN pin operates from an external supply that ranges from

6 V to 60 V and is the supply voltage for the internal linear

regulator of the ADP1974. Bypass the VIN pin to ground with a

4.7 μF or greater ceramic capacitor.

The VREG pin is the output of the internal linear regulator. The

internal regulator generates the 5 V (typical) rail that is used

internally to bias the control circuitry and can be used externally

as a pull-up voltage for the MODE, SYNC, DMAX, and FAULT

pins. Bypass the VREG pin to ground with a 1 μF ceramic

capacitor. VREG is disabled when EN is low and is active as

long as VIN is above the internal UVLO (5.71 V typical) and

EN is high.