ISSUED DATE :2003/05/20
REVISED DATE :2005/10/05C
GSC3842
Description
HIGH PERFORMANCE CURRENT MODE CONTROLERS
The GSC3842 is high performance fixed frequency current mode controllers. This is specifically designed for Off-Line and DC To DC
converter applications offering the designer a cost-effective solution with minimal external components.
These integrated circuits feature a trimmed oscillator for precise duty cycle control. A temperature compensated reference, high gain Error
amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET. Also Included are
protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting,
programmable output deadtime, and latch for single pulse metering.
*Trimmed Oscillator for Precise Frequency Control
*Oscillator Frequency Guaranteed at 250kHz
*Current Mode Operation to 500kHz
*Automatic Feed Forward Compensation
*latching PWM for Cycle-By-Cycle Current Limiting
*Internally Trimmed Reference with Undervoltage Lockout
*High Current Totem Pole Output
*Undervoltage Lockout with Hysteresis
*Low Startup and Operating Current
Features
Package Dimensions
REF.
A
B
C
D
E
F
Millimeter
Min.
Max.
5.80
4.80
3.80
0C
0.40
0.19
6.20
5.00
4.00
8C
0.90
0.25
REF.
M
H
L
J
K
G
Millimeter
Min.
Max.
0.10
0.25
0.35
0.49
1.35
1.75
0.375 REF.
45 C
1.27 TYP.
SOP-8L
Function
Pin1:Compensation
Pin2:Voltage Feedback
Pin3:Current Sense
Pin4:RT/CT
Pin5:Ground
Pin6:Output
Pin7:Vcc
Pin8:Vref
Description
This pin is the Error Amplifier output and is made available for loop
compensation.
This is the inverting input of the Error Amplifier. It’s normally connected to the
Switching power supply output through a resistor divider.
A voltage proportional to inductor current is connected to this input .The
PWM uses this information to terminate the output switch conduction.
The oscillator frequency and maximum output duty cycle are programmed by
connecting resistor RT to Vref and capacitor CT to ground .Operation 500kHz
is possible.
This pin is the combined control circuitry and power ground.
This output directly drives the gate of a power MOSFET. Peak currents up to
1 A are sourced and sunk by this pin.
This pin is the positive supply of the control IC.
This is the reference output .It provides charging current for capacitor CT
through resistor RT.
Absolute Maximum Ratings at Ta = 25 :
Parameter
Total power Supply and Zener current
Output current, source or sink(note1)
Output energy(capacitive load per cycle)
Current sense and voltage feedback inputs
Error Amplifier Output Sink Current
Symbol
(ICC+Iz)
Io
W
Vin
Io
Value
30
1.0
5.0
-0.3 to 5.5
10
Unit
mA
A
J
V
mA
GSC3842
Page: 1/9
GTM [ GTM CORPORATION ]
