Cherry Semiconductor CS2841BEN8, CS2841BEDR14, CS2841BED14 Datasheet

1

■ Optimized for

Off-line

Control

■ Internally Trimmed

Temperature
Compensated Oscillator

■ Maximum Duty-cycle

Clamp

■ V

REF

Stabilized before

Output Stage 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

8 Lead PDIP

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

V

CC

Pwr

V

OUT

Pwr Gnd
Gnd

14 Lead SO Narrow

CS2841B

Automotive Current Mode PWM

Control Circuit

CS2841B

Description

The CS2841B provides all the nec­essary features to implement off­line fixed frequency current-mode
control with a minimum number of
external components.

The CS2841B (a variation of the
CS-2843A) is designed specifically
for use in automotive operation.
The low start threshold voltage of

8.0V (typ), and the ability to sur­vive 40V automotive load dump
transients are important for auto­motive subsystem designs. The
CS-2841 series has a history of

quality and reliability in automo­tive applications.

The CS2841B incorporates a preci­sion temperature-controlled oscil­lator with an internally trimmed
discharge current to minimize vari­ations in frequency. Duty-cycles
greater than 50% are also possible.
On board logic ensures that V

REF

is
stabilized before the output stage
is enabled. Ion implant resistors
provide tighter control of under­voltage lockout.

Block Diagram

Absolute Maximum Ratings

Supply Voltage (Low Impedance Source)...................................................40V

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

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

Analog Inputs (V

FB

, Sense) ............................................................-0.3V to 5.5V

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

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

Features

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

Gnd

OSC

V

COMP

Sense

CC

8.0V/7.4V

+

FB

–

Amplifier

2.50V

Oscillator

Error

Undervoltage

Lock-out Circuit

V

C

2 R

R

Set/

Reset

Reference

Output
Enable

1 V

5V

Current

Sensing

Comparator

Internal

Bias

NOR

S

PWM

R

Latch

VCC Pwr

V

REF

V

OUT

Pwr Gnd

1

COMP

2

V

FB

3

Sense

4

OSC

8

V

7

V

6

V

5

Gnd

REF

CC

OUT

2

Electrical Characteristics: d -40≤TA≤85˚C RT=680kΩ, CT=0.022µF for triangular mode, VCC=15V (Note 1),

R

T

=10kΩ, CT=3.3nF for sawtooth mode (See Fig. 3), unless otherwise stated.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

CS2841B

Notes: 1. Adjust Vccabove the start threshold before setting at 15V. 3. Parameter measured at trip point of latch with VFB=0.

2.These parameters, although guaranteed, are not 100% tested in production. 4. Gain defined as:

A = ; 0 ≤ V

Sense

≤ 0.8V.

∆V

COMP

∆V

Sense

■ Reference Section

Output Voltage TJ=25˚C, I

OUT

=1mA 4.90 5.00 5.10 V
Line Regulation 8.4≤VCC≤16V 6 20 mV
Load Regulation 1≤I

OUT

≤20mA 6 25 mV
Temperature Stability (Note 2) 0.2 0.4 mV/˚C
Total Output Variation Line, Load, Temp. (Note 2) 4.82 5.18 V
Output Noise Voltage 10Hz≤f≤10kHz, TJ=25˚C (Note 2) 50 µV
Long Term Stability TA=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: (See Fig. 3)TJ=25˚C 47 52 57 kHz

Sawtooth Mode: -40˚C≤TA≤+85˚ 44 52 60 kHz

Triangular Mode (See Fig. 3) TJ=25˚C 44 52 60 kHz
Voltage Stability 8.4V≤Vcc≤16V 0.2 1.0 %
Temperature Stability Sawtooth Mode T

MIN≤TA≤TMAX

5%

Triangular Mode T

MIN≤TA≤TMAX

8%

(Note 2)
Amplitude V

OSC

(peak to peak) 1.7 V

Discharge current TJ=25˚C 7.4 8.3 9.2 mA

T

MIN≤TA≤TMAX

7.2 9.4 mA

■ Error Amp Section

Input Voltage V

COMP

=2.5V 2.42 2.50 2.58 V
Input Bias Current VFB=0V -0.3 -2.0 µA
A

VOL

2≤V

OUT

≤4V 65 90 dB
Unity Gain Bandwidth (Note 2) 0.7 1.0 MHz
PSRR 8.4V≤VCC≤16V 60 70 dB
Output Sink Current VFB=2.7V, V

COMP

=1.1V 2 6 mA

Output Source Current V

FB

=2.3V, V

COMP

=5V -0.5 -0.8 mA

V

OUT

High VFB=2.3V, RL=15kΩ to ground 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 12V≤VCC≤25V (Note 3) 70 dB
Input Bias Current V

Sense

=0V -2 -10 µA

Delay to Output T

J

=25˚C (Note 2) 150 300 ns