CS52843
CS52843
Current Mode PWM Control Circuit
Description
The CS52843 provides all the nec-
essary features to implement off-
line fixed frequency current-mode
control with a minimum number
of external components.
The CS52843 incorporates a new
precision temperature-controlled
oscillator to minimize variations in
frequency. An undervoltage lock-
out ensures that V
REF
is stabilized
before the output stage is enabled.
In the CS52843 turn on is at 8.4V
and turn off at 7.6V.
Other features include low start-up
current, pulse-by-pulse current lim-
iting, 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.
Features
s
Optimized for Off-line
Control
s
Internally Temperature
Compensated Oscillator
s
V
REF
Stabilized before
Output Stage is Enabled
s
Very Low Start-up Current
300 µA (typ)
s
Pulse-by-pulse Current
Limiting
s
Improved Undervoltage
Lockout
s
Double Pulse Suppression
s
2% 5 Volt Reference
s
High Current Totem Pole
Output
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
Block Diagram
V
CC
V
CC
Undervoltage Lock-out
V
CC
Pwr
Package Options
8L SO Narrow
COMP
V
FB
1
2
3
4
8
7
6
5
V
REF
V
CC
V
OUT
Gnd
34V
Gnd
8.4V/7.6V
V
FB
Error
Amplifier
-
+
2.50V
R
R
Set/
Reset
5.0 Volt
Reference
Internal
Bias
V
REF
Sense
OSC
14L SO Narrow
OUTPUT
ENABLE
COMP
COMP
1
NC
2
NOR
V
OUT
14
13
12
11
10
9
8
V
REF
NC
V
CC
V
CC
Pwr
V
OUT
Pwr Gnd
Gnd
OSC
Oscillator
S
V
FB
3
NC
4
2R
R
Sense
1V
Pwr Gnd
R
PWM
Current
Sensing Latch
Comparator
Sense
5
NC
6
OSC
7
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. 12/23/97
1
A
®
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
