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1
Features
Optimized for Off-line
Control
Internally Trimmed
Temperature
Compensated Oscillator
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
V
CC
Gnd
OSC
V
FB
COMP
Sense
V
REF
V
OUT
Output
Ref5V
Internal
Bias
NOR
S
R
PWM
Current
CSensing
Oscillator
1 V
R
2 R
V
C
AmError
+
–
2.50V
Set/
Undervoltage
Lock-out Circuit
34V
( ) Indicates CS-2843A/3843A
(16V/10V
V
CC
Pwr
Pwr Gnd
I
I
I
I
I
I
I
I
I
I
Package Options
C
Off-Line Current Mode PWM Control
Circuit with Undervoltage Lockout
Description
CS2842A/CS3842A
CS2843A/CS3843A
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
, 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
1
COMP
2
3
4
V
FB
Sense
OSC
V
REF
V
CC
V
OUT
Gnd
8
7
6
5
8 Lead PDIP & SO Narrow
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
The CS284XA, CS384XA provides all
the necessary features to implement
off-line fixed frequency current-mode
control with a minimum number of
external components.
The CS384XA family incorporates a
new precision temperature-controlled
oscillator with an internally trimmed
discharge current to minimize varia-
tions in frequency. A precision duty-
cycle clamp eliminates the need for an
external oscillator when a 50% duty-
cycle is used. 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 con-
trol of undervoltage lockout.
Other features include low start-up
current, pulse-by-pulse current limit-
ing, and a high-current totem pole out-
put for driving capacitive loads, such
as the gate of power MOSFET. The out-
put is LOW in the off state, consistent
with N-channel devices.
The CS384XA series of current-mode
control ICs are available in 8 and14
lead packages for surface mount (SO)
applications as well as 8 lead PDIP
packages.
A
Company
Rev. 10/23/98
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