top200-204-214 Power Integrations, Inc., top200-204-214 Datasheet - Page 3

• Manufacturer Part Number: top200-204-214
• Description: Three-terminal Off-line Pwm Switch
• Manufacturer: Power Integrations, Inc.

TOPSwitch Family Functional Description
TOPSwitch is a self biased and protected
linear control current-to-duty cycle
converter with an open drain output.
High efficiency is achieved through the
use of CMOS and integration of the
maximum number of functions possible.
CMOS significantly reduces bias
currents as compared to bipolar or
discrete solutions. Integration eliminates
external power resistors used for current
sensing and/or supplying initial start-up
bias current.
During normal operation, the internal
output MOSFET duty cycle linearly
decreases with increasing CONTROL
pin current as shown in Figure 4. To
implement all the required control, bias,
and protection functions, the DRAIN
and CONTROL pins each perform
several functions as described below.
Refer to Figure 2 for a block diagram
and Figure 6 for timing and voltage
waveforms of the TOPSwitch integrated
circuit.
Control Voltage Supply
CONTROL pin voltage V
or bias voltage for the controller and
driver circuitry. An external bypass
capacitor closely connected between the
CONTROL and SOURCE pins is
required to supply the gate drive current.
The total amount of capacitance
connected to this pin (C
auto-restart timing as well as control
loop compensation. V
either of two modes of operation.
Hysteretic regulation is used for initial
start-up and overload operation. Shunt
regulation is used to separate the duty
cycle error signal from the control circuit
supply current. During start-up, V
current is supplied from a high-voltage
switched current source connected
internally between the DRAIN and
CONTROL pins. The current source
provides sufficient current to supply the
control circuitry as well as charge the
total external capacitance (C
C
T
is regulated in
) also sets the
C
is the supply
T
).
C
Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.
Figure 5. Start-up Waveforms for (a) Normal Operation and (b) Auto-restart.
DRAIN
DRAIN
V C
V C
D MAX
D MIN
5.7 V
4.7 V
5.7 V
4.7 V
V IN
V IN
Auto-restart
0
0
0
0
I CD1
Charging C T
Charging C T
C
T
connected to the CONTROL pin
Off
Off
I C
I C
is the total external capacitance
2.5
Switching
I B
(a)
(b)
Discharging C T
I C (mA)
Slope = PWM Gain
Off
I CD1
95%
8 Cycles
Switching
-16%/mA
6.5
Switching
TOP200-4/14
5%
Discharging C T
I CD2
PI-1124A-060694
Off
PI-1691-112895
45
7/96
D
3