CS2841B
CS2841B
Automotive Current Mode PWM
Control Circuit
Description
The CS2841B provides all the nec-
essary features to implement off-
line 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 sur-
vive 40V automotive load dump
transients are important for auto-
motive subsystem designs. The
CS-2841 series has a history of
quality and reliability in automo-
tive applications.
The CS2841B incorporates a preci-
sion temperature-controlled oscil-
lator with an internally trimmed
discharge current to minimize vari-
ations 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 under-
voltage lockout.
Features
s
Optimized for Off-line
Control
s
Internally Trimmed
Temperature
Compensated Oscillator
s
Maximum Duty-cycle
Clamp
s
V
REF
Stabilized before
Output Stage Enabled
s
Low Start-up Current
s
Pulse-by-pulse Current
Limiting
s
Improved Undervoltage
Lockout
s
Double Pulse Suppression
s
1% Trimmed Bandgap
Reference
s
High Current Totem Pole
Output
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
Block Diagram
V
CC
Undervoltage
Lock-out Circuit
Set/
5V
Reset Reference
8.0V/7.4V
2.50V
OSC
Internal
Bias
Output
Enable
NOR
V
OUT
+
V
FB
Error
Amplifier
COMP
Sense
–
V
C
R
1 V
2 R
S
R
Current
Sensing
Comparator
PWM
Latch
Pwr Gnd
V
REF
Package Options
8 Lead PDIP
V
CC
Pwr
COMP
V
FB
Sense
OSC
1
2
3
4
8
7
6
5
V
REF
V
CC
V
OUT
Gnd
Gnd
14 Lead SO Narrow
COMP
1
NC
2
V
FB
3
NC
4
Sense
5
NC
6
OSC
7
14
13
12
11
10
9
8
V
REF
NC
V
CC
V
CC
Pwr
V
OUT
Pwr Gnd
Gnd
Oscillator
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 6/23/99
1
A
®
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
