Cherry Semiconductor CS3972YN8, CS3972YDWR16, CS3972YDW16, CS3972YTVA5, CS3972YTHA5 Datasheet

1

CS3972

1.25A High Efficiency Switching Regulator

CS3972

Description

Block Diagram

Features

■

75V

MAX

, 2A

PEAK

Internal

Switch

■

3V to 60V Input Voltage
Range

■

6mA Input Supply
Current

■

1.24V Precision Reference

■

40kHz Switching
Frequency

■

Variable Current Limit
with External Voltage
Clamp

■

Under-Voltage Protection

■

Over-Temperature
Protection

■

External Synchronization

Package Options

5L TO-220

Tab (Gnd)

8L PDIP

1

Gnd

V

C

V

FB

NC

E

2

V

SW

E

1

V

IN

1

1V

C

2V

FB

3 Gnd

4V

SW

5V

IN

16L SO Wide

1

GndNC
NC

NC

NC
V

IN

E

1

V

SW

E

2

V

C

V

FB

NC
NC
NC
NC
NC

The CS3972 is a 1.25A, 60V, current
mode, high efficiency, switching
regulator circuit. It can be config­ured in buck, boost, forward, iso­lated and non-isolated topologies,
using a single-ended switch.

The IC contains a 1.25A high effi­ciency output switch, precision
bandgap reference, voltage regula­tor, error amplifier, oscillator, con­trol, and protection circuitry.

Output transistor efficiency is
achieved by keeping the switch in
quasi-saturation when it is on. This
minimizes the switch turn-off
delay time and power dissipation,
an important consideration for
applications with wide ranging
loads.

The precision reference is internally
trimmed to 1.24V, while the oscilla­tor frequency is internally trimmed
to 40kHz. The on board 2.3V regu­lator powers the internal circuitry.
By keeping the voltage regulator at

2.3V, the IC is able to operate down
to 3V and maintain a constant input
supply current of 6mA(typ).

Synchronization mode is achieved
by applying a pulsating VCvoltage
of less than 0.2V with a duration of
about 0.5µs to VCpin. The switch­ing frequency can be adjusted from
50kHz to 70kHz. The IC's synchro­nization mode is set externally.

Protection circuitry includes a vari­able current limit with external
voltage clamp, under-voltage and
over-temperature protection.

Rev. 6/23/99

Cherry Semiconductor Corporation

2000 South County Trail, East Greenwich, RI 02818

Tel: [phone] Fax: [phone]

Email: [e-mail]

Web Site: www.cherry-semi.com

A Company

®

V

IN

2.3V
Reg

Output

Protection

V

SW

0.22Ω

1.25A,
75V

Switch

E2*
E1*

Gnd

40kHz

OSC

V

C

1.24V
Ref

-

+

Error
Amp

V

FB

*Always connect E1 to Ground Pin on DIP package. Both emitters are tied to ground on TO-220 Package.

COMP

+

Logic

Driver

-

+

Current

0.22Ω

Amp

-

2

Absolute Maximum Ratings

CS3972

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Input Voltage Range ........................................................................................................................................................3V to 60V

Output Switching Voltage.........................................................................................................................................................75V

Voltage Transient (t

r

=10µs, tf=400ms)......................................................................................................................................60V

ESD (Human Body Model; R=1.5kΩ, C=100pF) ...................................................................................................................2kV

Junction Temperature Range...............................................................................................................................-40°C to +150°C

Storage Temperature Range ................................................................................................................................-65°C to +150°C

Lead Temperature Soldering

Wave Solder (through hole styles only)......................................................................................10 sec. max, 260°C peak

Reflow (SMD styles only) ......................................................................................60 sec. max above 183°C, 230°C peak

Feedback Pin Voltage (1ms transient)...................................................................................................................................±15V

Electrical Characteristics:

For 3V≤VCC≤60V, -40°C≤TA≤125°C unless otherwise specified.

■

Reference Voltage VC=0.8V; VFB=V

REF

1.214 1.244 1.274 V

Line Regulation VC=0.8V; VFB=V

REF

, 3V≤VIN≤60V 0.03 %/V

Feedback Input Current VC=0.8V; VFB=V

REF

350 1100 nA

Minimum Input Voltage VC=VFB=V

REF

2.6 3.0 V
Supply Current VC=0.6V; 3V≤VIN≤60V 6.0 9.0 mA
Supply Current Increase

during switch on time VC=open, 1.0V≤VFB≤1.5V 25 mA/A

Switching Frequency VC=VFB=V

REF; VSW

=15V 33 40 47 kHz
Maximum Duty Cycle VC=2V; VFB=open, VSW=15V 92 %
VCThreshold VFB=open; VSW=15V, 0.60 0.90 1.25 V

duty cycle=0%

■ Error Amplifier

Transconductance VC=0.8V; VFB=V

REF

, ∆IC=±25µA 2400 4400 7000 µmho
Source/Sink Current VC=1.5V 120 200 400 µA
High Voltage Clamp VFB=1.0V 2.0 V
Low Voltage Clamp VFB=1.5V 0.38 V
Gain 0.9V≤VC≤1.4V, VFB=V

REF

800 V/V

■ Output Switch

Breakdown Voltage VC=0.5V; 3V≤VIN≤60V, I

OUT

=5mA 75 90 V

On Resistance VC=open, VFB=0.8V, I

OUT

=1.25A 0.6 1.0 Ω

Control Voltage to Switch 1.2V≤VC≤1.8V 2 A/V

Current Transconductance

Current Limit Duty Cycle≤50%, TJ≥25°C 1.25 3.00 A

Duty Cycle≤50%, TJ<25°C 1.25 3.50 A
Duty Cycle=80% 1.00 2.50 A
Duty Cycle=80% (Note 1) 0.50 2.50 A

Note 1: 16 lead SO wide package only.