Figure 1. Typical Flyback Application.

PRODUCT3Adapter1Open

Frame2Open

Frame2

OUTPUT POWER TABLE

Table 1. Notes: 1. Typical continuous power in a non-ventilated

enclosed adaptor measured at 50 ˚C ambient. 2. Maximum practical

105 W 205 W 70 W 155 W

120 W 250 W 80 W 180 W

Lower System Cost, High Design Flexibility

• Line over-voltage (OV) shutdown extends line surge limit

reduction rejects line ripple and limits DCMAX at high line

• Regulates to zero load without dummy loading

• 132 kHz frequency reduces transformer/power supply size

• Half frequency option in Y package for video applications

• Hysteretic thermal shutdown for automatic fault recovery

• Allows shutdown/wake-up via LAN/input port

TOPSwitch-GX uses the same proven topology as TOPSwitch,

cost effectively integrating the high voltage power MOSFET,

PWM control, fault protection and other control circuitry onto

a single CMOS chip. TOPSwitch-GX extends beyond the power

ranges of existing TOPSwitch families while integrating many

new functions that are designed to reduce system cost and

improve design flexibility, performance and energy efficiency.

Depending on package type, the TOPSwitch-GX family has

All package types provide the following transparent features:

Soft-start, 132 kHz switching frequency (automatically reduced

at light load), frequency jittering for lower EMI, wider DCMAX,

hysteretic thermal shutdown and larger creepage packages. In

addition, all critical parameters (i.e. current limit, frequency,

PWM gain) have tighter temperature and absolute tolerance, to

Functional Block Diagram......................................................................................................................................... 3

Error Amplifier .........................................................................................................................................................7

On-chip Current Limit with External Programmability.............................................................................................7

Line Under-Voltage Detection (UV) ........................................................................................................................8

Line Over-Voltage Shutdown (OV) ......................................................................................................................... 8

Line Feed Forward with DCMAX Reduction ..............................................................................................................8

Remote ON/OFF and Synchronization...................................................................................................................9

Soft-Start ................................................................................................................................................................9

Shutdown/Auto-Restart ..........................................................................................................................................9

Hysteretic Over-Temperature Protection ................................................................................................................9

Bandgap Reference................................................................................................................................................9

Typical Uses of FREQUENCY (F) Pin ......................................................................................................................15

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins....................................................... 16

Typical Uses of MULTI-FUNCTION (M) Pin .............................................................................................................19

Application Examples...............................................................................................................................................21

A High Efficiency, 30 W, Universal Input Power Supply........................................................................................ 21

A High Efficiency, Enclosed, 70 W, Universal Adapter Supply..............................................................................22

A High Efficiency, 250 W, 250 - 380 VDC Input Power Supply............................................................................. 23

Multiple Output, 60 W, 185 - 265 VAC Input Power Supply..................................................................................24

Processor Controlled Supply Turn On/Off ............................................................................................................25

Key Application Considerations.............................................................................................................................. 27

Product Specifications and Test Conditions .......................................................................................................... 33

Typical Performance Characteristics ...................................................................................................................... 40

Part Ordering Information ........................................................................................................................................44

Package Outlines ......................................................................................................................................................44

Error amplifier and feedback current input pin for duty cycle

control. Internal shunt regulator connection to provide internal

bias current during normal operation. It is also used as the

connection point for the supply bypass and auto-restart/

compensation capacitor.

LINE-SENSE (L) Pin: (Y package only)

Input pin for OV, UV, line feed forward with DCMAX reduction,

remote ON/OFF and synchronization. A connection to SOURCE

pin disables all functions on this pin.

EXTERNAL CURRENT LIMIT (X) Pin: (Y package only)

one pin. Input pin for OV, UV, line feed forward with DCMAX

reduction, external current limit adjustment, remote ON/OFF

and synchronization. A connection to SOURCE pin disables all

functions on this pin and makes TOPSwitch-GX operate in

simple three terminal mode (like TOPSwitch-II).

FREQUENCY (F) Pin: (Y package only)

Figure 3. Pin Configuration (top view).

is required to supply the instantaneous gate drive current. The

approximately 5.8 V, the control circuitry is activated and the

duty cycle of the MOSFET from zero to the maximum value

over approximately 10 ms. If no external feedback/supply

current is fed into the CONTROL pin by the end of the soft-start,

the high voltage current source is turned off and the CONTROL

pin will start discharging in response to the supply current

drawn by the control circuitry. If the power supply is designed

properly, and no fault condition such as open loop or shorted

in excess of the consumption of the chip is shunted to SOURCE

CONTROL pin capacitance sets the dominant pole for the

control loop.

When a fault condition such as an open loop or shorted output

prevents the flow of an external current into the CONTROL pin,

the capacitor on the CONTROL pin discharges towards 4.8 V.

At 4.8 V, auto-restart is activated which turns the output

MOSFET off and puts the control circuitry in a low current

standby mode. The high-voltage current source turns on and

supply under-voltage comparator keeps VC within a window of

typically 4.8 to 5.8 V by turning the high-voltage current source

on and off as shown in Figure 8. The auto-restart circuit has a

divide-by-8 counter which prevents the output MOSFET from

This is accomplished by enabling the output MOSFET only

when the divide-by-8 counter reaches full count (S7). The

counter effectively limits TOPSwitch-GX power dissipation by

reducing the auto-restart duty cycle to typically 4%. Auto-

The nominal switching frequency of 132 kHz was chosen to

minimize transformer size while keeping the fundamental EMI

frequency below 150 kHz. The FREQUENCY pin (available

only in TO-220 package), when shorted to the CONTROL pin,

lowers the switching frequency to 66 kHz (half frequency)

which may be preferable in some cases such as noise sensitive

the FREQUENCY pin should be connected to the SOURCE pin

for the default 132 kHz.

To further reduce the EMI level, the switching frequency is

by driving the output MOSFET with a duty cycle inversely

proportional to the current into the CONTROL pin that is in

excess of the internal supply current of the chip (see Figure 7).

The excess current is the feedback error signal that appears

across RE (see Figure 2). This signal is filtered by an RC

network with a typical corner frequency of 7 kHz to reduce the

effect of switching noise in the chip supply current generated by

the MOSFET gate driver. The filtered error signal is compared

with the internal oscillator sawtooth waveform to generate the

duty cycle waveform. As the control current increases, the duty

value of 78% (typical). However, by connecting the LINE-

to the rectified DC high voltage bus through a resistor with

appropriate value, the maximum duty cycle can be made to

decrease from 78% to 38% (typical) as shown in Figure 11 when

input line voltage increases (see line feed forward with DCMAX

Light Load Frequency Reduction

The pulse width modulator duty cycle reduces as the load at the

power supply output decreases. This reduction in duty cycle is

typically 30 kHz and 15 kHz for 132 kHz and 66 kHz operation,

at light loads thus lowering the switching losses while

maintaining good cross regulation performance and low output

Error Amplifier

The shunt regulator can also perform the function of an error

amplifier in primary side feedback applications. The shunt

regulator voltage is accurately derived from a temperature-

On-chip Current Limit with External Programmability

The cycle-by-cycle peak drain current limit circuit uses the

output MOSFET ON-resistance as a sense resistor. A current

limit comparator compares the output MOSFET on-state drain

to source voltage, VDS(ON) with a threshold voltage. High drain

current causes VDS(ON) to exceed the threshold voltage and turns

the output MOSFET off until the start of the next clock cycle.

The current limit comparator threshold voltage is temperature

compensated to minimize the variation of the current limit due

to temperature related changes in RDS(ON) of the output MOSFET.

the MOSFET will be disabled during the next cycle (see figure 8).

The same resistor used for UV and OV also implements line

current into the LINE-SENSE pin or out from the EXTERNAL

It also allows for microprocessor controlled turn-on and turn-

effectively minimizes current and voltage stresses on the output

MOSFET, the clamp circuit and the output rectifier during start-

up. This feature also helps minimize output overshoot and

I

Figure 18. Line-Sensing for Under-Voltage Only (Over-

Voltage Disabled). Maximum Duty Cycle will be

reduced at Low Line.

Figure 20. Externally Set Current Limit. Figure 21. Current Limit Reduction with Line Voltage.

Figure 22. Active-on (Fail Safe) Remote ON/OFF.

Figure 28. Line-Sensing and Externally Set Current Limit.

V

V

A High Efficiency, 30 W, Universal Input Power Supply

The circuit shown in Figure 41 takes advantage of several of the

30 W at 12 V, from an 85 to 265 VAC input, at an ambient of

of a smaller transformer core size and/or higher transformer

TOPSwitch-GX power dissipation, while at the same time

avoiding transformer core saturation during startup and output

transient conditions. The resistors R1 & R2 provide a signal

that reduces the current limit with increasing line voltage,

which in turn limits the maximum overload power at high input

soft-start feature of TOPSwitch-GX, allows the use of a low cost

RCD clamp (R3, C3 and D1) with a higher reflected voltage, by

safely limiting the TOPSwitch-GX drain voltage, with adequate

margin under worst case conditions. Resistor R4 provides line

sensing, setting UV at 100 VDC and OV at 450 VDC. The

(guaranteed minimum value of 75% vs. 64% for TOPSwitch-II)

allows the use of a smaller input capacitor (C1). The extended

maximum duty cycle and the higher reflected voltage possible

with the RCD clamp also permit the use of a higher primary to

secondary turns ratio for T1 which reduces the peak reverse

voltage experienced by the secondary rectifier D8. As a result

reduction feature of the TOPSwitch-GX eliminates the need for

any dummy loading for regulation at no load and reduces the no

load/standby consumption of the power supply. Frequency

jitter provides improved margin for conducted EMI meeting the

CISPR 22 (FCC B) specification.

Output regulation is achieved by using a simple Zener sense

circuit for low cost. The output voltage is determined by the

Zener diode (VR2) voltage and the voltage drops across the

optocoupler (U2) LED and resistor R6. Resistor R8 provides

bias current to Zener VR2 for typical regulation of ±5% at the

12 V output level, over line and load and component variations.

Due to the thermal environment of a sealed adapter a TOP249Y