TK75001 Datasheet, PDF (1/13 Pages) TOKO, Inc – PWM CONTROLLER

TK75001
PWM CONTROLLER
FEATURES
s Optimized for Off-Line Operation
s Maximum Duty Ratio 44% (typ.)
s Maximum Clock Frequency Above 1 MHz
s Frequency Reduction for Improved Overcurrent
Protection
s Low Standby Current for Current-Fed Start-Up
s Current-Mode or Voltage-Mode Control
s Internal User-Adjustable Slope Compensation
s Functionally Integrated & Simplified 5-pin Design
DESCRIPTION
APPLICATIONS
s Off-Line Power Supplies
s Industrial Power Supplies
s Telecom Power Supplies
s Off-Line Battery Chargers
The TK75001 is a simplified primary side controller
optimized for off-line switching power supplies. It is suitable
for both voltage-mode and current-mode control and has
advanced features not available in controllers with a higher
pin count. The key to full functionality in a 5-pin design is
that the current signal and the error signal are added
together and fed into the feedback pin. A sawtooth current
flowing out of the feedback pin provides a slope
compensation ramp (in current-mode applications) or a
PWM ramp (in voltage-mode applications), in proportion to
the resistance terminating that pin. If the sum of the current
sense signal, error signal and ramp signal exceeds the
Overcurrent Detector threshold indicating that the Current
Control Detector has lost control of the switch current, the
charging current of the timing capacitor will be reduced to
about 25% for the remainder of the clock period. The
reduced charging current causes no more than a one-third
reduction in switching frequency, effectively preventing
short-circuit current runaway.
The TK75001 is available in an 8-pin DIP package.
ORDERING INFORMATION
TK75001D
Tape/Reel Code
Temperature Code
TEMP. CODE (OPTIONAL)
I: -40 to +85 C
TAPE/REEL CODE
MG: Magazine
TK75001
75001
DRV
GND
GND
CT
VCC
NC
NC
FB
Note: Pins 2 and 3 must be externally
connected for proper operation.
BLOCK DIAGRAM
VCC
ICT
CT
IFR
146 µA
ICHG
205 µA
IDS
2 mA
OSCILLATOR
BANDGAP
REFERENCE
fCLK
UVLO
14.5 V
10.5 V
17.5 V
R
FREQUENCY
Q
REDUCTION
LATCH
S
TOGGLE FF
T
Q
SLOPE
COMPENSATION
PWM LATCH
S
OVERCURRENT
DETECTOR
Q
R
1.35 V
CURRENT
CONTROL
FB
DETECTOR
0.98 V
DRV
GND
January 1999 TOKO, Inc.
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