Cherry Semiconductor CS52845EDR8, CS52845EDR14, CS52845ED8, CS52845ED14 Datasheet

The CS52845 provides all the nec­essary features to implement off­line fixed frequency current-mode
control with a minimum number
of external components.

The CS52845 incorporates a new
precision temperature-controlled
oscillator to minimize variations in
frequency. An internal toggle flip­flop, which blanks the output
every other clock cycle, limits the
duty-cycle range to less than 50%.

An undervoltage lockout ensures
that V

REF

is stabilized before the
output stage is enabled. In the
CS52845 turn on is at 8.4V and
turn off at 7.6V.

Other features include low start-up
current, pulse-by-pulse current lim­iting, and a high-current totem pole
output for driving capacitive loads,
such as gate of a power MOSFET.
The output is low in the off state,
consistent with N-channel devices.

1

Features

■

Optimized for Off-line
Control

■

Temperature
Compensated Oscillator

■

50% Maximum Duty-cycle
Clamp

■ V

REF

Stabilized before

Output Stage is Enabled

■ Low Start-up Current

■ Pulse-by-pulse Current

Limiting

■ Improved Undervoltage

Lockout

■ Double Pulse Suppression

■ 1% Trimmed Bandgap

Reference

■ High Current Totem Pole

Output

Package Options

CS52845

Current Mode PWM

Control Circuit

with 50% Max Duty Cycle

CS52845

Description

Block Diagram

Absolute Maximum Ratings

Supply Voltage (I

CC

<30mA) ..........................................................Self Limiting

Supply Voltage (Low Impedance Source)...................................................30V

Output Current ...............................................................................................±1A

Output Energy (Capacitive Load) .................................................................5µJ

Analog Inputs (V

FB

, V

SENSE

)...........................................................-0.3V to 5.5V

Error Amp Output Sink Current...............................................................10mA

Lead Temperature Soldering

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

10

7

14

13

12

8

1

2

3

4

5

6

11

9

COMP

NC

V

FB

NC

Sense

NC

OSC

V

REF

NC
V

CC

VCC Pwr
V

OUT

Pwr Gnd

Gnd

14L SO Narrow

7

8

2

3

4

5

6

COMP

V

FB

Sense

OSC

V

REF

V

CC

V

OUT

Gnd

8L SO Narrow

Rev. 3/4/99

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

Undervoltage Lock-out

V

CC

CC

V

Pwr

CC

1

34V

Gnd

8.4V/7.6V

V

FB

COMP

OSC

Sense

Error

Amplifier

2 R

­+

2.50V

Oscillator

R

1V

Undervoltage

R

R

Current

Sensing

Comparator

Set/

Reset

V

REF

Lockout

Toggle

Flip-Flop

S

R
PWM

Latch

5.0 Volt

Reference

NOR

Internal

Bias

V

REF

V

OUT

Pwr Gnd

2

Electrical Characteristics: -40 ≤ TA ≤ 85˚C; V

CC

= 15V (Note 1); RT = 10kΩ; CT = 3.3nF for sawtooth mode.unless otherwise stated.

CS52845

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

■ Reference Section

Output Voltage TJ=25˚C, I

REF

=1mA 4.95 5.00 5.05 V

Line Regulation 12≤V

CC

≤25V 6 20 mV

Load Regulation 1≤I

REF

≤20mA 6 25 mV

Temperature Stability (Note 2) 0.2 0.4 mV/˚C

Total Output Variation Line, Load, Temp. (Note 2) 4.90 5.10 V

Output Noise Voltage 10Hz≤f≤10kHz, T

J

=25˚C (Note 2) 50 µV

Long Term Stability T

A

=125˚C, 1000 Hrs. (Note 2) 5 25 mV

Output Short Circuit TA=25˚C -30 -100 -180 mA

■ Oscillator Section

Initial Accuracy Sawtooth Mode, T

J

=25˚C475257kHz

Voltage Stability 12≤V

CC

≤25V 0.2 1.0 %

Temperature Stability Sawtooth Mode T

MIN≤TA≤TMAX

(Note 2) 5 %

Amplitude V

OSC

(peak to peak) 1.7 V

■ Error Amp Section

Input Voltage V

COMP

=2.5V 2.45 2.50 2.55 V

Input Bias Current VFB=0V -0.3 -1.0 µA

A

VOL

2≤V

OUT

≤4V 65 90 dB

Unity Gain Bandwidth (Note 2) 0.7 1.0 MHz

PSRR 12≤VCC≤25V 60 70 dB

Output Sink Current VFB=2.7V, V

COMP

=1.1V 2 6 mA

Output Source Current VFB=2.3V, V

COMP

=5V -0.5 -0.8 mA

V

OUT

HIGH VFB=2.3V, RL=15kΩ to Gnd 5 6 V

V

OUT

LOW VFB=2.7V, RL=15kΩ to V

REF

0.7 1.1 V

■ Current Sense Section

Gain (Notes 3 & 4) 2.85 3.00 3.15 V/V

Maximum Input Signal V

COMP

=5V (Note 3) 0.9 1.0 1.1 V

PSRR 12≤V

CC

≤25V (Note 3) 70 dB

Input Bias Current V

Sense

=0V -2 -10 µA

Delay to Output TJ=25˚C (Note 2) 150 300 ns

■ Output Section

Output Low Level I

SINK

=20mA 0.1 0.4 V

I

SINK

=200mA 1.5 2.2 V

Output High Level I

SOURCE

=20mA 13.0 13.5 V

I

SOURCE

=200mA 12.0 13.5 V

Rise Time TJ=25˚C, CL=1nF (Note 2) 50 150 ns

Fall Time TJ=25˚C, CL=1nF (Note 2) 50 150 ns