CS2842A Datasheet, PDF (1/6 Pages) Cherry Semiconductor Corporation – Off-Line Current Mode PWM Control Circuit with Undervoltage Lockout

CS2842A/CS3842A
CS2843A/CS3843A
Off-Line Current Mode PWM Control
Circuit with Undervoltage Lockout
Description
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.
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
Block Diagram
V_CC
Gnd
OSC
V_FB
COMP
Sense
Undervoltage
Lock-out Circuit
34V
Set/
5V
Reset Reference
16V/10V
(8.4V/7.6V)
2.50V
Output
Enable
Oscillator
Internal
Bias
NOR
+
–
Error
V_C
Amplifier
2R
R
S
R
1 V Current
Sensing
Comparator
PWM
Latch
( ) Indicates CS-2843A/3843A
V_CC Pwr
V_REF
V_OUT
Pwr Gnd
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 is 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
Package Options
8 Lead PDIP & SO Narrow
COMP 1
V_FB 2
Sense 3
OSC 4
8 V_REF
7 V_CC
6 V_OUT
5 Gnd
14 Lead SO Narrow
COMP 1
NC 2
V_FB 3
NC 4
Sense 5
NC 6
OSC 7
14 V_REF
13 NC
12 V_CC
11 V_CC Pwr
10 V_OUT
9 Pwr Gnd
8 Gnd
Rev. 10/23/98
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: [phone] Fax: [phone]
Email: [e-mail]
Web Site: www.cherry-semi.com
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