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

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.

3

Package Pin Description

PACKAGE PIN # PIN SYMBOL FUNCTION

Typical Performance Characteristics

Reference Voltage vs. Temperature

Switching Frequency vs. Temperature

Driver Current vs. Switch Current

97

96

95

93

92

91

90

-50 -25 -0 25 50 75 100 125 150

Junction Temperature (°C)

Duty Cycle (%)

Maximum Duty Cycle

Switch Saturation Voltage

16L 5L 8L

SO Wide TO-220 PDIP

16 3 1 Gnd Logic and power ground on TO-220. Logic ground only on 8L

PDIP.

21 2 VCControl voltage can be used for frequency compensation, cur-

rent limit threshold, frequency synchronization, and soft start.

32 3 VFBFeedback voltage is the negative input to the error amplifier.

1,4,5,6,7,8, 4 NC No connection.

10,12,15

95 5 VINSupply input voltage with a range of 3V to 60V.

11 6 E

1

Emitter One is a power ground which should always be con­nected to logic ground since it is used as the negative input to
the current sense amp.

13 4 7 V

SW

Collector of internal 75V NPN power switch.

14 8 E

2

Emitter Two is a power ground which can be left disconnected
to reduce the switch rating to 625mA.

CS3972

1.274

1.264

1.254

1.244

1.234

1.224

Reference Voltage (V)

1.214

-50 -25 -0 25 50 75 100 125 150

Temperature (°C)

47

45

43
41

39

37

Frequency (kHz)

35

33

-50 -25 -0 25 50 75 100 125 150

Temperature (°C)

100

90
80
70
60

50
40

30
20

Driver Current (mA)

10

0

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Switch Current (A)

1.8 2.0

1.6
Tj=25°C

1.4

1.2

1.0

0.8

0.6

0.4

0.2

Switch Saturation Voltage (V)

0

0.25 0.75 1.50

0 0.50 1.00 1.25 1.75

Switch Current (A)

2.0

The CS3972 has an on board, high current NPN transistor
in its output stage. The output transistor is switched on
every 25µs by the on board 40 kHz oscillator. The output
is switched off as soon as the output current reaches a
dynamically controlled level. That level is determined by
three factors: the current drawn by the load, the input
voltage, and the output voltage. This control scheme has
several benefits. The IC reacts quickly to overvoltage and
short circuit conditions and it is less sensitive to input
voltage fluctuation.

Current drawn by the load influences when the output
stage turns off. The voltage across the internal high preci­sion resistor (0.11Ω) in the emitter of the output transistor
generating the input to the current sensing amplifier. The
output of the current sensing amplifier provides one of the
inputs to the comparator.

The other input to the comparator connected to the out­put of the error amplifier whose inverting input is con­nected to the output voltage through the feedback circuit­ry while its noninverting input is set to an internal refer­ence voltage of 1.24V. When the current sensing amplifier
output exceeds the error amplifier output, the comparator
switches off, triggering the logic which turns off the out­put stage.

All on board amplifier, logic and protection circuitry uses
the internal 2.3V reference to minimize quiescent current
drain (6mA) and permits IC operation down to 3V.

The anti-saturation circuitry minimizes output switch
turn off time and power dissipation, by keeping the
power NPN at the edge of saturation.

4

Circuit Description

Application Diagrams

Figure 1: Boost Regulator Figure 2: Buck Regulator with the External Switch

Figure 3: Flyback Multiple Output Regulator

Figure 4: Isolated Forward Regulator

CS3972

L

V

IN

1

V

SW

V

IN

CS3972

V

+

C

1

C

R

1

C

Gnd

2

D

1

V

FB

R

2

(1.24V)

+

R

3

V

OUT

C

3

V

IN

R

1

+

C

1

R

Q

1

V

SW

V

IN

V

CS3972

V

C

2

C

2

FB

Gnd

D

L

1

R

3

(1.24V)

R

1

4

V

OUT

+

C

3

Gnd

TR

1

R

V

FB

(1.24V)

R

V

IN

C

4

R

1

C

1

V

SW

V

IN

CS3972

V

+

C

C

2

R

2

C

3

V

OUT

1

+V

+

C

5

V

OUT

2

+

C

6

4

5

IN

V

SW

V

+

C

2

–V

IN

IN

CS3972

R

1

V

C

R

2

V

FB

Gnd

1/2

OC1

C

D

3

1

TR

D

1

1

D

2

D

3

1/2

OC1

U

1

R

3

L

1

R

4

V

OUT

+

C

3

C

5

R

5

R

6

C

4

R

7

Thermal Data 5L 8L 16L

TO-220 PDIP SO Wide

R

ΘJC

typ 1.7 52 23 ˚C/W

R

ΘJA

typ 50 100 105 ˚C/W

D

Lead Count Metric English

Max Min Max Min

8 Lead PDIP 10.16 9.02 .400 .355

16 Lead SO Wide 10.50 10.10 .413 .398

5

CS3972

Package Specification

PACKAGE DIMENSIONS IN mm (INCHES)

PACKAGE THERMAL DATA

Plastic DIP (N); 300 mil wide

0.39 (.015)
MIN.

2.54 (.100) BSC

1.77 (.070)

1.14 (.045)

D

Some 8 and 16 lead
packages may have
1/2 lead at the end
of the package.
All specs are the same.

.203 (.008)

.356 (.014)

REF: JEDEC MS-001

3.68 (.145)

2.92 (.115)

8.26 (.325)

7.62 (.300)

7.11 (.280)

6.10 (.240)

.356 (.014)

.558 (.022)

Surface Mount Wide Body (DW); 300 mil wide

1.27 (.050) BSC

7.60 (.299)

7.40 (.291)

10.65 (.419)

10.

00 (.394)

D

0.32 (.013)

0.23 (.009)

1.27 (.050)

0.40 (.016)

REF: JEDEC MS-013

2.49 (.098)

2.24 (.088)

0.51 (.020)

0.33 (.013)

2.65 (.104)

2.35 (.093)

0.30 (.012)

0.10 (.004)

6

Package Specification

Ordering Information

Rev. 6/23/99

CS3972

Part Number Description

CS3972YN8 8L PDIP
CS3972YDW16 16L SO Wide
CS3972YDWR16 16L SO Wide (tape & reel)
CS3972YT5 TO-220 Straight
CS3972YTVA5 TO-220 Vertical
CS3972YTHA5 TO-220 Horizontal

© 1999 Cherry Semiconductor Corporation

Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.

5 Lead TO-220 (T) Straight

2.87 (.113)

2.62 (.103)

6.93(.273)

6.68(.263)

9.78 (.385)

10.54 (.415)

1.02(.040)

0.63(.025)

1.83(.072)

1.57(.062)

0.56 (.022)

0.36 (.014)

2.92 (.115)

2.29 (.090)

1.40 (.055)

1.14 (.045)

4.83 (.190)

4.06 (.160)

6.55 (.258)

5.94 (.234)

14.22 (.560)

13.72 (.540)

1.02 (.040)

0.76 (.030)

3.71 (.146)

3.96 (.156)

14.99 (.590)

14.22 (.560)

5 Lead TO-220 (TVA) Vertical

1.68
(.066) typ

1.70 (.067)

7.51 (.296)

1.78 (.070)

4.34 (.171)

0.56 (.022)

0.36 (.014)

1.40 (.055)

1.14 (.045)

4.83 (.190)

4.06 (.160)

14.99 (.590)

14.22 (.560)

2.92 (.115)

2.29 (.090)

.94 (.037)
.69 (.027)

8.64 (.340)

7.87 (.310)

6.80 (.268)

10.54 (.415)

9.78 (.385)

2.87 (.113)

2.62 (.103)

6.55 (.258)

5.94 (.234)

3.96 (.156)

3.71 (.146)

5 Lead TO-220 (THA) Horizontal

0.81(.032)

1.70 (.067)

6.81(.268)

1.40 (.055)

1.14 (.045)

5.84 (.230)

6.60 (.260)

6.83 (.269)

0.56 (.022)

0.36 (.014)

10.54 (.415)

9.78 (.385)

6.55 (.258)

5.94 (.234)

3.96 (.156)

3.71 (.146)

1.68

(.066)

TYP

14.99 (.590)

14.22 (.560)

2.77 (.109)

2.29 (.090)

2.92 (.115)

4.83 (.190)

4.06 (.160)

2.87 (.113)

2.62 (.103)