®
Figure 1. Typical Flyback Application.
PRODUCT3Adapter1Open
Frame2Open
Frame2
OUTPUT POWER TABLE
Table 1. Notes: 1. Typical continuous power in a non-ventilated
enclosed adapter measured at 50 °C ambient. 2. Maximum practical
continuous power in an open frame design at 50 °C ambient. See
Key Applications for detailed conditions. 3. See Part Ordering
Information. 4. 230 VAC or 100/115 VAC with doubler.
PI-2632-060200
AC
IN DC
OUT
D
S
C
TOPSwitch-GX
CONTROL
L
+
-
FX
230 VAC ±15%4
Adapter1
85-265 VAC
9 W 15 W 6.5 W 10 W
21 W 22 W 11 W 14 W
10 W 22 W 7 W 14 W
13 W 25 W 9 W 15 W
29 W 45 W 17 W 23 W
20 W 45 W 15 W 30 W
16 W 30 W 11 W 20 W
34 W 50 W 20 W 28 W
30 W 65 W 20 W 45 W
37 W 57 W 23 W 33 W
40 W 85 W 26 W 60 W
40 W 64 W 26 W 38 W
60 W 125 W 40 W 90 W
42 W 70 W 28 W 43 W
85 W 165 W 55 W 125 W
43 W 75 W 30 W 48 W
105 W 205 W 70 W 155 W
44 W 79 W 31 W 53 W
120 W 250 W 80 W 180 W
45 W 82 W 32 W 55 W
135 W 290 W 90 W 210 W
Product Highlights
Lower System Cost, High Design Flexibility
Extended power range to 290 W
Features eliminate or reduce cost of external components
Fully integrated soft-start for minimum stress/overshoot
Externally programmable accurate current limit
•Wider duty cycle for more power, smaller input capacitor
Separate line sense and current limit pins on Y/R/F packages
Line under-voltage (UV) detection: no turn off glitches
Line overvoltage (OV) shutdown extends line surge limit
Line feed forward with maximum duty cycle (DCMAX)
reduction rejects line ripple and limits DCMAX at high line
Frequency jittering reduces EMI and EMI filtering costs
Regulates to zero load without dummy loading
132 kHz frequency reduces transformer/power supply size
Half frequency option in Y/R/F packages for video applications
Hysteretic thermal shutdown for automatic fault recovery
Large thermal hysteresis prevents PC board overheating
EcoSmart
-
Energy Efficient
Extremely low consumption in remote off mode
(80 mW @ 110 VAC, 160 mW @ 230 VAC)
Frequency lowered with load for high standby efficiency
Allows shutdown/wake-up via LAN/input port
Description
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. Many new functions are integrated to re-
duce system cost and improve design flexibility, performance
and energy efficiency.
Depending on package type, the TOPSwitch-GX family has
either 1 or 3 additional pins over the standard DRAIN, SOURCE
and CONTROL terminals allowing the following functions: line
sensing (OV/UV, line feedforward/DC max reduction), accu-
rate externally set current limit, remote on/off, and synchroni-
zation to an external lower frequency and frequency selection
(132 kHz/66 kHz).
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
simplify design and optimize system cost.
TOP242 P or G
TOP242 R
TOP242 Y or F
TOP243 P or G
TOP243 R
TOP243 Y or F
TOP244 P or G
TOP244 R
TOP244 Y or F
TOP245 R
TOP245 Y or F
TOP246 R
TOP246 Y or F
TOP247 R
TOP247 Y or F
TOP248 R
TOP248 Y or F
TOP249 R
TOP249 Y or F
TOP250 R
TOP250 Y or F
®
®
TOP242-250
TOPSwitch
-
GX
Family
Extended Power, Design Flexible,
EcoSmart
, Integrated Off-line Switcher
September 2002
TOP242-250
2
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Section List
Functional Block Diagram......................................................................................................................................... 3
Pin Functional Description........................................................................................................................................ 4
TOPSwitch-GX
Family Functional Description ........................................................................................................5
CONTROL (C) Pin Operation .................................................................................................................................6
Oscillator and Switching Frequency .......................................................................................................................6
Pulse Width Modulator and Maximum Duty Cycle .................................................................................................7
Light Load Frequency Reduction............................................................................................................................7
Error Amplifier.........................................................................................................................................................7
On-chip Current Limit with External Programmability.............................................................................................7
Line Under-Voltage Detection (UV) ........................................................................................................................8
Line Overvoltage 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
High-Voltage Bias Current Source........................................................................................................................10
Using Feature Pins.................................................................................................................................................... 11
FREQUENCY (F) Pin Operation........................................................................................................................... 11
LINE-SENSE (L) Pin Operation............................................................................................................................ 11
EXTERNAL CURRENT LIMIT (X) Pin Operation ................................................................................................. 11
MULTI-FUNCTION (M) Pin Operation ..................................................................................................................12
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
TOPSwitch-II
vs.
TOPSwitch-GX..........................................................................................................................
27
TOPSwitch-FX vs. TOPSwitch-GX .......................................................................................................................
28
TOPSwitch-GX
Design Considerations ................................................................................................................29
TOPSwitch-GX
Layout Considerations.................................................................................................................31
Quick Design Checklist.........................................................................................................................................31
Design Tools .........................................................................................................................................................33
Product Specifications and Test Conditions ..........................................................................................................34
Typical Performance Characteristics ......................................................................................................................41
Part Ordering Information ........................................................................................................................................45
Package Outlines ......................................................................................................................................................45
TOP242-250
3
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9/02
Figure 2a. Functional Block Diagram (Y, R or F Package).
PI-2641-061200
PI-2639-060600
Figure 2b. Functional Block Diagram (P or G Package).
PI-2631-061200
SHUTDOWN/
AUTO-RESTART
PWM
COMPARATOR
CLOCK
SAW
CONTROLLED
TURN-ON
GATE DRIVER
CURRENT LIMIT
COMPARATOR
INTERNAL UV
COMPARATOR
INTERNAL
SUPPLY
5.8 V
4.8 V
SOURCE (S)
S
R
Q
DMAX
STOP SOFT-
START
-
+
CONTROL (C)
MULTI-
FUNCTION (M)
-
+
5.8 V
IFB
RE
ZC
VC
+
-
LEADING
EDGE
BLANKING
÷ 8
1
HYSTERETIC
THERMAL
SHUTDOWN
SHUNT REGULATOR/
ERROR AMPLIFIER
+
-
DRAIN (D)
ON/OFF
SOFT
START
DCMAX
VBG
DCMAX
VBG + VT
0
OV/UV
VI (LIMIT)
CURRENT
LIMIT
ADJUST
LINE
SENSE
SOFT START
LIGHT LOAD
FREQUENCY
REDUCTION
STOP LOGIC
OSCILLATOR WITH JITTER
PI-2639-060600
SHUTDOWN/
AUTO-RESTART
PWM
COMPARATOR
CLOCK
SAW
HALF
FREQ.
CONTROLLED
TURN-ON
GATE DRIVER
CURRENT LIMIT
COMPARATOR
INTERNAL UV
COMPARATOR
INTERNAL
SUPPLY
5.8 V
4.8 V
SOURCE (S)
S
R
Q
DMAX
STOP SOFT-
START
-
+
CONTROL (C)
LINE-SENSE (L)
EXTERNAL
CURRENT LIMIT (X)
FREQUENCY (F)
-
+
5.8 V
1 V
IFB
RE
ZC
VC
+
-
LEADING
EDGE
BLANKING
÷ 8
1
HYSTERETIC
THERMAL
SHUTDOWN
SHUNT REGULATOR/
ERROR AMPLIFIER +
-
DRAIN (D)
ON/OFF
SOFT
START
DCMAX
VBG
DCMAX
VBG + VT
0
OV/UV
V
I (LIMIT)
CURRENT
LIMIT
ADJUST
LINE
SENSE
SOFT START
LIGHT LOAD
FREQUENCY
REDUCTION
STOP LOGIC
OSCILLATOR WITH JITTER
TOP242-250
4
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9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Pin Functional Description
DRAIN (D) Pin:
High voltage power MOSFET drain output. The internal
start-up bias current is drawn from this pin through a switched
high-voltage current source. Internal current limit sense point
for drain current.
CONTROL (C) Pin:
Error amplifier and feedback current input pin for duty cycle
control. Internal shunt regulator connection to provide inter-
nal 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, R or F 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, R or F
package only)
Input pin for external current limit adjustment, remote
ON/OFF, and synchronization. A connection to SOURCE pin
disables all functions on this pin.
MULTI-FUNCTION (M) Pin: (P or G package only)
This pin combines the functions of the LINE-SENSE (L) and
EXTERNAL CURRENT LIMIT (X) pins of the Y package
into 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).
Figure 3. Pin Configuration (top view).
PI-2509-040501
DC
Input
Voltage
+
-
DM
S
C
VUV = IUV x RLS
VOV = IOV x RLS
For RLS = 2 M
VUV = 100 VDC
VOV = 450 VDC
DCMAX@100 VDC = 78%
DCMAX@375 VDC = 38%
CONTROL
R
LS
2 M
PI-2517-040501
DC
Input
Voltage
+
-
DM
S
C
For RIL = 12 k
ILIMIT = 69%
CONTROL
RIL
See fig. 55 for other
resistor values (RIL)
For RIL = 25 k
ILIMIT = 43%
to select different
ILIMIT values
X
PI-2629-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
RIL
RLS
12 k
2 M
VUV = IUV x RLS
VOV = IOV x RLS
For RLS = 2 M
DCMAX@100 VDC = 78%
DCMAX@375 VDC = 38%
For RIL = 12 k
ILIMIT = 69%
See fig. 55 for other
resistor values (RIL)
to select different ILIMIT
values
VUV = 100 VDC
VOV = 450 VDC
Figure 4. Y/R/F Package Line Sense and Externally Set Current
Limit.
Figure 5. P/G Package Line Sense.
Figure 6. P/G Package Externally Set Current Limit.
FREQUENCY (F) Pin: (Y, R or F package only)
Input pin for selecting switching frequency: 132 kHz if
connected to SOURCE pin and 66 kHz if connected to
CONTROL pin. The switching frequency is internally set for
fixed 132 kHz operation in P and G packages.
SOURCE (S) Pin:
Output MOSFET source connection for high voltage power
return. Primary side control circuit common and reference point.
PI-2724-010802
Tab Internally
Connected to
SOURCE Pin
Y Package (TO-220-7C)
CD
S
S
S
S
1 C
3 X
2 L
5 F
4 S
7 D
M
P Package (DIP-8B)
G Package (SMD-8B)
R Package (TO-263-7C)
F Package (TO-262-7C)
8
5
7
1
12345 7
CLXSF D
4
2
3
TOP242-250
5
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9/02
TOPSwitch-GX
Family Functional Description
Like TOPSwitch, TOPSwitch-GX is an integrated switched
mode power supply chip that converts a current at the control
input to a duty cycle at the open drain output of a high voltage
power MOSFET. During normal operation the duty cycle of
the power MOSFET decreases linearly with increasing
CONTROL pin current as shown in Figure 7.
In addition to the three terminal TOPSwitch features, such as
the high voltage start-up, the cycle-by-cycle current limiting,
loop compensation circuitry, auto-restart, thermal shutdown,
the TOPSwitch-GX incorporates many additional functions that
reduce system cost, increase power supply performance and
design flexibility. A patented high voltage CMOS technology
allows both the high voltage power MOSFET and all the low
voltage control circuitry to be cost effectively integrated onto
a single monolithic chip.
Three terminals, FREQUENCY, LINE-SENSE, and EXTER-
NAL CURRENT LIMIT (available in Y, R or F package) or
one terminal MULTI-FUNCTION (available in P or G
Package) have been added to implement some of the new
functions. These terminals can be connected to the SOURCE
pin to operate the TOPSwitch-GX in a TOPSwitch-like three
terminal mode. However , even in this three terminal mode, the
TOPSwitch-GX offers many new transparent features that do
not require any external components:
1. A fully integrated 10 ms soft-start limits peak currents and
voltages during start-up and dramatically reduces or
eliminates output overshoot in most applications.
2. DCMAX of 78% allows smaller input storage capacitor, lower
input voltage requirement and/or higher power capability.
3. Frequency reduction at light loads lowers the switching
losses and maintains good cross regulation in multiple
output supplies.
4. Higher switching frequency of 132 kHz reduces the
transformer size with no noticeable impact on EMI.
5. Frequency jittering reduces EMI.
6. Hysteretic over-temperature shutdown ensures automatic
recovery from thermal fault. Large hysteresis prevents circuit
board overheating.
7. Packages with omitted pins and lead forming provide large
drain creepage distance.
8. Tighter absolute tolerances and smaller temperature vari-
ations on switching frequency, current limit and PWM gain.
The LINE-SENSE (L) pin is usually used for line sensing by
connecting a resistor from this pin to the rectified DC high
voltage bus to implement line overvoltage (OV), under-voltage
(UV) and line feed forward with DCMAX reduction. In this
mode, the value of the resistor determines the OV/UV thresholds
and the DCMAX is reduced linearly starting from a line voltage
above the under-voltage threshold. See Table 2 and Figure 11.
The pin can also be used as a remote ON/OFF and a
synchronization input.
The EXTERNAL CURRENT LIMIT (X) pin is usually used to
reduce the current limit externally to a value close to the operat-
ing peak current, by connecting the pin to SOURCE through a
resistor. This pin can also be used as a remote ON/OFF and a
synchronization input in both modes. See Table 2 and Figure 1 1.
For the P or G packages the LINE-SENSE and EXTERNAL
CURRENT LIMIT pin functions are combined on one MULTI-
FUNCTION (M) pin. However , some of the functions become
mutually exclusive as shown in Table 3.
The FREQUENCY (F) pin in the Y, R or F package sets the
switching frequency to the default value of 132 kHz when
connected to SOURCE pin. A half frequency option of 66 kHz
can be chosen by connecting this pin to CONTROL pin
instead. Leaving this pin open is not recommended.
PI-2633-011502
Duty Cycle (%)
I
C
(mA)
TOP242-5 1.6 2.0
TOP246-9 2.2 2.6
TOP250 2.4 2.7
5.2 6.0
5.8 6.6
6.5 7.3
I
CD1
I
B
Auto-restart
I
L
= 125 µA
I
L
< I
L(DC)
I
L
= 190 µA
78
10
38
Frequency (kHz)
I
C
(mA)
30
I
CD1
I
B
Auto-restart
132
Note: For P and G packages I
L
is replaced with I
M
.
I
L
< I
L(DC)
I
L
= 125 µA
Slope = PWM Gain
I
L
= 190 µA
Figure 7. Relationship of Duty Cycle and Frequency to CONTROL
Pin Current.
TOP242-250
6
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
PI-2545-082299
S1 S2 S6 S7 S1 S2 S6 S7S0 S1 S7
S0 S0 5.8 V
4.8 V
S7
0 V
0 V
0 V
V
LINE
V
C
V
DRAIN
V
OUT
Note: S0 through S7 are the output states of the auto-restart counter
2
1234
0 V
~
~
~
~
~
~~
~~
~
S6 S7
~
~~
~
~
~
~
~
V
UV
~
~
~
~
~
~
~
~
S2
~
~
CONTROL (C) Pin Operation
The CONTROL pin is a low impedance node that is capable of
receiving a combined supply and feedback current. During
normal operation, a shunt regulator is used to separate the feed-
back signal from the supply current. CONTROL pin voltage
VC is the supply voltage for the control circuitry including the
MOSFET gate driver. An external bypass capacitor closely
connected between the CONTROL and SOURCE pins is
required to supply the instantaneous gate drive current. The
total amount of capacitance connected to this pin also sets the
auto-restart timing as well as control loop compensation.
When rectified DC high voltage is applied to the DRAIN pin
during start-up, the MOSFET is initially off, and the
CONTROL pin capacitor is charged through a switched high
voltage current source connected internally between the DRAIN
and CONTROL pins. When the CONTROL pin voltage VC
reaches approximately 5.8 V, the control circuitry is activated
and the soft-start begins. The soft-start circuit gradually
increases the duty cycle of the MOSFET from zero to the maxi-
mum 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 output exists, the feedback loop will close, providing
external CONTROL pin current, before the CONTROL pin
voltage has had a chance to discharge to the lower threshold
voltage of approximately 4.8 V (internal supply under-voltage
lockout threshold). When the externally fed current charges
the CONTROL pin to the shunt regulator voltage of 5.8 V, cur -
rent in excess of the consumption of the chip is shunted to
SOURCE through resistor RE as shown in Figure 2. This
current flowing through RE controls the duty cycle of the power
MOSFET to provide closed loop regulation. The shunt
regulator has a finite low output impedance ZC that sets the
gain of the error amplifier when used in a primary feedback
configuration. The dynamic impedance Z C of the CONTROL
pin together with the external 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
charges the external capacitance again. A hysteretic internal
supply under-voltage comparator keeps VC within a window
of typically 4.8 V 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-eight counter which prevents the out-
put MOSFET from turning on again until eight discharge/charge
cycles have elapsed. This is accomplished by enabling the
output MOSFET only when the divide-by-eight counter reaches
full count (S7). The counter effectively limits TOPSwitch-GX
power dissipation by reducing the auto-restart duty cycle to
typically 4%. Auto-restart mode continues until output
voltage regulation is again achieved through closure of the
feedback loop.
Oscillator and Switching Frequency
The internal oscillator linearly charges and discharges an
internal capacitance between two voltage levels to create a
sawtooth waveform for the pulse width modulator. This
Figure 8. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down.
TOP242-250
7
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9/02
Figure 9. Switching Frequency Jitter (Idealized VDRAIN waveform).
oscillator sets the pulse width modulator/current limit latch at
the beginning of each cycle.
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 Y, R or F 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
video applications or a high efficiency standby mode. Other-
wise, 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
jittered (frequency modulated) by approximately ±4 kHz at
250 Hz (typical) rate as shown in Figure 9. Figure 46 shows
the typical improvement of EMI measurements with frequency
jitter.
Pulse Width Modulator and Maximum Duty Cycle
The pulse width modulator implements voltage mode control
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 cycle decreases. A clock signal from the
oscillator sets a latch which turns on the output MOSFET . The
pulse width modulator resets the latch, turning off the output
MOSFET. Note that a minimum current must be driven into
the CONTROL pin before the duty cycle begins to change.
The maximum duty cycle, DCMAX, is set at a default maximum
value of 78% (typical). However, by connecting the LINE-
SENSE or MULTI-FUNCTION pin (depending on the
package) 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 reduction).
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 proportional to the current flowing into the CONTROL pin.
As the CONTROL pin current increases, the duty cycle
decreases linearly towards a duty cycle of 10%. Below 10%
duty cycle, to maintain high efficiency at light loads, the
frequency is also reduced linearly until a minimum frequency
is reached at a duty cycle of 0% (refer to Figure 7). The
minimum frequency is typically 30 kHz and 15 kHz for
132 kHz and 66 kHz operation, respectively.
This feature allows a power supply to operate at lower
frequency at light loads thus lowering the switching losses while
maintaining good cross regulation performance and low
output ripple.
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-
compensated bandgap reference. The gain of the error ampli-
fier is set by the CONTROL pin dynamic impedance. The
CONTROL pin clamps external circuit signals to the VC
voltage level. The CONTROL pin current in excess of the
supply current is separated by the shunt regulator and flows
through RE as a voltage error signal.
On-chip Current Limit with External Programmability
The cycle-by-cycle peak drain current limit circuit uses the out-
put 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 default current limit of TOPSwitch-GX is preset internally.
However, with a resistor connected between EXTERNAL
CURRENT LIMIT (X) pin (Y, R or F package) or MULTI-
FUNCTION (M) pin (P or G package) and SOURCE pin,
current limit can be programmed externally to a lower level
between 30% and 100% of the default current limit. Please refer
to the graphs in the typical performance characteristics section
for the selection of the resistor value. By setting current limit
low, a larger TOPSwitch-GX than necessary for the power
required can be used to take advantage of the lower RDS(ON) for
higher efficiency/smaller heat sinking requirements. With a
second resistor connected between the EXTERNAL
PI-2550-092499
128 kHz
4 ms
Time
Switching
Frequency
V
DRAIN
136 kHz
TOP242-250
8
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Figure 10. Synchronization Timing Diagram.
PI-2637-060600
Oscillator
(SAW)
DMAX
Enable from
X, L or M Pin (STOP) Time
CURRENT LIMIT (X) pin (Y, R or F package) or MULTI-
FUNCTION (M) pin (P or G package) and the rectified DC
high voltage bus, the current limit is reduced with increasing
line voltage, allowing a true power limiting operation against
line variation to be implemented. When using an RCD clamp,
this power limiting technique reduces maximum clamp
voltage at high line. This allows for higher reflected voltage
designs as well as reducing clamp dissipation.
The leading edge blanking circuit inhibits the current limit
comparator for a short time after the output MOSFET is turned
on. The leading edge blanking time has been set so that, if a
power supply is designed properly, current spikes caused by
primary-side capacitances and secondary-side rectifier reverse
recovery time should not cause premature termination of the
switching pulse.
The current limit is lower for a short period after the leading
edge blanking time as shown in Figure 52. This is due to
dynamic characteristics of the MOSFET. To avoid triggering
the current limit in normal operation, the drain current wave-
form should stay within the envelope shown.
Line Under-Voltage Detection (UV)
At power up, UV keeps TOPSwitch-GX off until the input line
voltage reaches the under voltage threshold. At power down,
UV prevents auto-restart attempts after the output goes out of
regulation. This eliminates power down glitches caused by
the slow discharge of large input storage capacitor present in
applications such as standby supplies. A single resistor
connected from the LINE-SENSE pin (Y, R or F package) or
MULTI-FUNCTION pin (P or G package) to the rectified DC
high voltage bus sets UV threshold during power up. Once the
power supply is successfully turned on, the UV threshold is
lowered to 40% of the initial UV threshold to allow extended
input voltage operating range (UV low threshold). If the UV
low threshold is reached during operation without the power
supply losing regulation the device will turn off and stay off
until UV (high threshold) has been reached again. If the power
supply loses regulation before reaching the UV low threshold,
the device will enter auto-restart. At the end of each auto-
restart cycle (S7), the UV comparator is enabled. If the UV high
threshold is not exceeded the MOSFET will be disabled during
the next cycle (see Figure 8). The UV feature can be disabled
independent of OV feature as shown in Figures 19 and 23.
Line Overvoltage Shutdown (OV)
The same resistor used for UV also sets an overvoltage thresh-
old which, once exceeded, will force TOPSwitch-GX output
into off-state. The ratio of OV and UV thresholds is preset at
4.5 as can be seen in Figure 1 1. When the MOSFET is off, the
rectified DC high voltage surge capability is increased to the
voltage rating of the MOSFET (700 V), due to the absence of
the reflected voltage and leakage spikes on the drain. A small
amount of hysteresis is provided on the OV threshold to
prevent noise triggering. The OV feature can be disabled
independent of the UV feature as shown in Figures 18 and 32.
Line Feed Forward with DCMAX Reduction
The same resistor used for UV and OV also implements line
voltage feed forward which minimizes output line ripple and
reduces power supply output sensitivity to line transients. This
feed forward operation is illustrated in Figure 7 by the
different values of IL (Y, R or F package) or IM (P or G Pack-
age). Note that for the same CONTROL pin current, higher
line voltage results in smaller operating duty cycle. As an added
feature, the maximum duty cycle DCMAX is also reduced from
78% (typical) at a voltage slightly higher than the UV thresh-
old to 30% (typical) at the OV threshold (see Figures 7 and
11). Limiting DCMAX at higher line voltages helps
TOP242-250
9
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9/02
prevent transformer saturation due to large load transients in
forward converter applications. DCMAX of 38% at the OV thresh-
old was chosen to ensure that the power capability of the
TOPSwitch-GX is not restricted by this feature under normal
operation.
Remote ON/OFF and Synchronization
TOPSwitch-GX can be turned on or off by controlling the current
into the LINE-SENSE pin or out from the EXTERNAL
CURRENT LIMIT pin (Y, R or F package) and into or out from
the MULTI-FUNCTION pin (P or G package) (see Figure 11).
In addition, the LINE-SENSE pin has a 1 V threshold compara-
tor connected at its input. This voltage threshold can also be used
to perform remote ON/OFF control. This allows easy implemen-
tation of remote ON/OFF control of TOPSwitch-GX in several
different ways. A transistor or an optocoupler output connected
between the EXTERNAL CURRENT LIMIT or LINE-SENSE
pins (Y, R or F package) or the MULTI-FUNCTION pin (P or G
package) and the SOURCE pin implements this function with
“active-on” (Figures 22, 29 and 36) while a transistor or an
optocoupler output connected between the LINE-SENSE pin
(Y, R or F package) or the MUL TI-FUNCTION (P or G package)
pin and the CONTROL pin implements the function with
“active-off” (Figures 23 and 37).
When a signal is received at the LINE-SENSE pin or the
EXTERNAL CURRENT LIMIT pin (Y, R or F package) or
the MULTI-FUNCTION pin (P or G package) to disable the
output through any of the pin functions such as OV, UV and
remote ON/OFF, TOPSwitch-GX always completes its current
switching cycle, as illustrated in Figure 10, before the output is
forced off. The internal oscillator is stopped slightly before the
end of the current cycle and stays there as long as the disable
signal exists. When the signal at the above pins changes state
from disable to enable, the internal oscillator starts the next
switching cycle. This approach allows the use of these pins to
synchronize TOPSwitch-GX to any external signal with a
frequency between its internal switching frequency and 20 kHz.
As seen above, the remote ON/OFF feature allows the
TOPSwitch-GX to be turned on and off instantly, on a cycle-
by-cycle basis, with very little delay. However, remote
ON/OFF can also be used as a standby or power switch to turn
off the TOPSwitch-GX and keep it in a very low power
consumption state for indefinitely long periods. If the
TOPSwitch-GX is held in remote off state for long enough time
to allow the CONTROL pin to dishcharge to the internal
supply under-voltage threshold of 4.8 V (approximately 32 ms
for a 47 µF CONTROL pin capacitance), the CONTROL pin
goes into the hysteretic mode of regulation. In this mode, the
CONTROL pin goes through alternate charge and discharge
cycles between 4.8 V and 5.8 V (see CONTROL pin operation
section above) and runs entirely off the high voltage DC input,
but with very low power consumption (160 mW typical at
230 VAC with M or X pins open). When the TOPSwitch-GX is
remotely turned on after entering this mode, it will initiate a
normal start-up sequence with soft-start the next time the
CONTROL pin reaches 5.8 V. In the worst case, the delay from
remote on to start-up can be equal to the full discharge/char ge
cycle time of the CONTROL pin, which is approximately
125 ms for a 47 µF CONTROL pin capacitor. This
reduced consumption remote off mode can eliminate
expensive and unreliable in-line mechanical switches. It also
allows for microprocessor controlled turn-on and turn-off
sequences that may be required in certain applications such as
inkjet and laser printers.
Soft-Start
Two on-chip soft-start functions are activated at start-up with
a duration of 10 ms (typical). Maximum duty cycle starts from
0% and linearly increases to the default maximum of 78% at
the end of the 10 ms duration and the current limit starts from
about 85% and linearly increases to 100% at the end of the
10ms duration. In addition to start-up, soft-start is also
activated at each restart attempt during auto-restart and when
restarting after being in hysteretic regulation of CONTROL
pin voltage (VC), due to remote off or thermal shutdown
conditions. This 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 prevents saturation of the
transformer during start-up.
Shutdown/Auto-Restart
To minimize TOPSwitch-GX power dissipation under fault
conditions, the shutdown/auto-restart circuit turns the power
supply on and off at an auto-restart duty cycle of typically 4%
if an out of regulation condition persists. Loss of regulation
interrupts the external current into the CONTROL pin. VC regu-
lation changes from shunt mode to the hysteretic auto-restart
mode as described in CONTROL pin operation section. When
the fault condition is removed, the power supply output
becomes regulated, VC regulation returns to shunt mode, and
normal operation of the power supply resumes.
Hysteretic Over-Temperature Protection
Temperature protection is provided by a precision analog
circuit that turns the output MOSFET off when the junction
temperature exceeds the thermal shutdown temperature
(140 °C typical). When the junction temperature cools to
below the hysteretic temperature, normal operation resumes
providing automatic recovery. A large hysteresis of 70 °C
(typical) is provided to prevent overheating of the PC board
due to a continuous fault condition. VC is regulated in hyster-
etic mode and a 4.8 V to 5.8 V (typical) sawtooth waveform is
present on the CONTROL pin while in thermal shutdown.
Bandgap Reference
All critical TOPSwitch-GX internal voltages are derived from
a temperature-compensated bandgap reference. This reference
TOP242-250
10
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9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
is also used to generate a temperature-compensated current
reference which is trimmed to accurately set the switching
frequency, MOSFET gate drive current, current limit, and the
line OV/UV thresholds. TOPSwitch-GX has improved circuitry
to maintain all of the above critical parameters within very tight
absolute and temperature tolerances.
High-Voltage Bias Current Source
This current source biases TOPSwitch-GX from the DRAIN
pin and charges the CONTROL pin external capacitance
during start-up or hysteretic operation. Hysteretic operation
occurs during auto-restart, remote off and over-temperature
shutdown. In this mode of operation, the current source is
switched on and off with an effective duty cycle of approxi-
mately 35%. This duty cycle is determined by the ratio of
CONTROL pin charge (IC) and discharge currents (ICD1 and
ICD2). This current source is turned off during normal
operation when the output MOSFET is switching. The effect
of the current source switching will be seen on the DRAIN
voltage waveform as small disturbances and is normal.
TOP242-250
11
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9/02
FREQUENCY (F) Pin Operation
The FREQUENCY pin is a digital input pin available in the
Y, R or F package only. Shorting the FREQUENCY pin to
SOURCE pin selects the nominal switching frequency of
132 kHz (Figure 13) which is suited for most applications. For
other cases that may benefit from lower switching
frequency such as noise sensitive video applications, a 66 kHz
switching frequency (half frequency) can be selected by
shorting the FREQUENCY pin to the CONTROL pin
(Figure 14). In addition, an example circuit shown in Figure 15
may be used to lower the switching frequency from 132 kHz in
normal operation to 66 kHz in standby mode for very low standby
power consumption.
LINE-SENSE (L) Pin Operation (Y, R and F Packages)
When current is fed into the LINE-SENSE pin, it works as a
voltage source of approximately 2.6 V up to a maximum
current of +400 µA (typical). At +400 µA, this pin turns into a
constant current sink. Refer to Figure 12a. In addition, a
comparator with a threshold of 1 V is connected at the pin and is
used to detect when the pin is shorted to the SOURCE pin.
There are a total of four functions available through the use of
the LINE-SENSE pin: OV, UV, line feed forward with DCMAX
reduction, and remote ON/OFF. Connecting the LINE-SENSE
pin to the SOURCE pin disables all four functions. The LINE-
SENSE pin is typically used for line sensing by connecting a
resistor from this pin to the rectified DC high voltage bus to imple-
ment OV, UV and DCMAX reduction with line voltage. In this
mode, the value of the resistor determines the line OV/UV thresh-
olds, and the DCMAX is reduced linearly with rectified DC high
voltage starting from just above the UV threshold. The pin can
also be used as a remote on/off and a synchronization input. Refer
to Table 2 for possible combinations of the functions with
Using Feature Pins
✔✔ ✔✔✔
✔✔ ✔✔✔
✔✔✔
✔✔ ✔✔ ✔✔
✔✔✔✔✔
16 17 18 19 20 21 22 23 24 25 26 27 28 29
Table 2. Typical LINE-SENSE and EXTERNAL CURRENT LIMIT Pin Configurations.
*This table is only a partial list of many LINE-SENSE and EXTERNAL CURRENT LIMIT pin configurations that are possible.
Figure Number
Three Terminal Operation
Under-Voltage
Overvoltage
Line Feed Forward (DCMAX)
Overload Power Limiting
External Current Limit
Remote ON/OFF
example circuits shown in Figure 16 through Figure 40. A
description of specific functions in terms of the LINE-SENSE
pin I/V characteristic is shown in Figure 11 (right hand side).
The horizontal axis represents LINE-SENSE pin current with
positive polarity indicating currents flowing into the pin. The
meaning of the vertical axes varies with functions. For those
that control the on/off states of the output such as UV, OV and
remote ON/OFF, the vertical axis represents the enable/
disable states of the output. UV triggers at IUV (+50 µA typical
with 30 µA hysteresis) and OV triggers at IOV (+225 µA
typical with 8 µA hysteresis). Between the UV and OV thresh-
olds, the output is enabled. For line feed forward with DCMAX
reduction, the vertical axis represents the magnitude of the
DCMAX. Line feed forward with DCMAX reduction lowers
maximum duty cycle from 78% at IL(DC) (+60 µA typical) to
38% at IOV (+225 µA).
EXTERNAL CURRENT LIMIT (X) Pin Operation
(Y, R and F Packages)
When current is drawn out of the EXTERNAL CURRENT
LIMIT pin, it works as a voltage source of approximately
1.3 V up to a maximum current of –240 µA (typical). At
–240 µA, it turns into a constant current source (refer to
Figure 12a).
There are two functions available through the use of the
EXTERNAL CURRENT LIMIT pin: external current limit
and remote ON/OFF . Connecting the EXTERNAL CURRENT
LIMIT pin and SOURCE pin disables the two functions. In
high efficiency applications this pin can be used to reduce the
current limit externally to a value close to the operating peak
current, by connecting the pin to the SOURCE pin through a
resistor. The pin can also be used for remote on/off. Table 2
shows several possible combinations using this pin. See
LINE-SENSE AND EXTERNAL CURRENT LIMIT PIN TABLE*
TOP242-250
12
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9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
✔✔
✔✔
✔✔
✔✔ ✔✔
✔✔
Table 3. Typical MULTI-FUNCTION Pin Configurations.
MULTI-FUNCTION PIN TABLE*
30 31 32 33 34 35 36 37 38 39 40
Figure Number
Three Terminal Operation
Under-Voltage
Overvoltage
Line Feed Forward (DCMAX)
Overload Power Limiting
External Current Limit
Remote ON/OFF
Figure 1 1 for a description of the functions where the horizon-
tal axis (left hand side) represents the EXTERNAL CURRENT
LIMIT pin current. The meaning of the vertical axes varies
with function. For those that control the on/off states of the
output such as remote ON/OFF, the vertical axis represents the
enable/disable states of the output. For external current limit,
the vertical axis represents the magnitude of the ILIMIT. Please
see graphs in the typical performance characteristics section
for the current limit programming range and the selection of
appropriate resistor value.
MULTI-FUNCTION (M) Pin Operation (P and G Packages)
The LINE-SENSE and EXTERNAL CURRENT LIMIT pin
functions are combined to a single MULTI-FUNCTION pin
for P and G packages. The comparator with a 1 V threshold at
the LINE-SENSE pin is removed in this case as shown in
Figure 2b. All of the other functions are kept intact. However,
since some of the functions require opposite polarity of input
current (MULTI-FUNCTION pin), they are mutually
exclusive. For example, line sensing features cannot be used
simultaneously with external current limit setting. When
current is fed into the MULTI-FUNCTION pin, it works as a
voltage source of approximately 2.6 V up to a maximum
current of +400 µA (typical). At +400 µA, this pin turns into a
constant current sink. When current is drawn out of the MULTI-
FUNCTION pin, it works as a voltage source of
approximately 1.3 V up to a maximum current of –240 µA
(typical). At –240 µA, it turns into a constant current source.
Refer to Figure 12b.
There are a total of five functions available through the use of
the MULTI-FUNCTION pin: OV, UV, line feed forward with
DCMAX reduction, external current limit and remote ON/OFF.
A short circuit between the MULTI-FUNCTION pin and
SOURCE pin disables all five functions and forces
TOPSwitch-GX to operate in a simple three terminal mode like
TOPSwitch-II. The MULTI-FUNCTION pin is typically used
for line sensing by connecting a resistor from this pin to the
rectified DC high voltage bus to implement OV, UV and DCMAX
reduction with line voltage. In this mode, the value of the
resistor determines the line OV/UV thresholds, and the DCMAX
is reduced linearly with rectified DC high voltage starting from
just above the UV threshold. In high efficiency applications
this pin can be used in the external current limit mode instead,
to reduce the current limit externally to a value close to the
operating peak current, by connecting the pin to the SOURCE
pin through a resistor. The same pin can also be used as a
remote on/off and a synchronization input in both modes. Please
refer to Table 3 for possible combinations of the functions with
example circuits shown in Figure 30 through Figure 40. A
description of specific functions in terms of the MULTI-
FUNCTION pin I/V characteristic is shown in Figure 11. The
horizontal axis represents MUL TI-FUNCTION pin current with
positive polarity indicating currents flowing into the pin. The
meaning of the vertical axes varies with functions. For those
that control the on/off states of the output such as UV, OV and
remote ON/OFF, the vertical axis represents the enable/
disable states of the output. UV triggers at IUV (+50 µA
typical) and OV triggers at IOV (+225 µA typical with 30 µA
hysteresis). Between the UV and OV thresholds, the output is
enabled. For external current limit and line feed forward with
DCMAX reduction, the vertical axis represents the magnitude of
the ILIMIT and DCMAX. Line feed forward with DCMAX reduction
lowers maximum duty cycle from 78% at IM(DC) (+60 µA
typical) to 38% at IOV (+225 µA). External current limit is
available only with negative MULTI-FUNCTION pin current.
Please see graphs in the typical performance characteristics
section for the current limit programming range and the
selection of appropriate resistor value.
*This table is only a partial list of many MULTI-FUNCTION pin configurations that are possible.
TOP242-250
13
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9/02
Figure 11. MULTI-FUNCTION (P or G package), LINE-SENSE, and EXTERNAL CURRENT LIMIT (Y, R or F package) Pin Characteristics.
-250 -200 -150 -100 -50 0 50 100 150 200 250 300 350 400
PI-2636-010802
Output
MOSFET
Switching
(Enabled)
(Disabled)
I
LIMIT
(Default)
DC
MAX
(78.5%)
Current
Limit
M Pin
L PinX Pin
Maximum
Duty Cycle
V
BG
-22 µA
-27 µAV
BG
+ V
TP
I
I
I
I
I
UV
I
REM(N)
I
OV
Pin Voltage
Note: This figure provides idealized functional characteristics with typical performance values. Please refer to the parametric
table and typical performance characteristics sections of the data sheet for measured data.
X and L Pins (Y, R or F Package) and M Pin (P or G Package) Current (µA)
Disabled when supply
output goes out of
regulation
TOP242-250
14
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Figure 12a. LINE-SENSE (L), and EXTERNAL CURRENT LIMIT (X) Pin Input Simplified Schematic.
Figure 12b. MULTI-FUNCTION (M) Pin Input Simplified Schematic.
V
BG
+ V
T
1 V
V
BG
240 µA
400 µA
CONTROL Pin
Y, R and F Package
(Voltage Sense)
(Positive Current Sense - Under-Voltage,
Overvoltage, ON/OFF Maximum Duty
Cycle Reduction)
(Negative Current Sense - ON/OFF,
Current Limit Adjustment)
PI-2634-010802
TOPSwitch-GX
LINE-SENSE (L)
EXTERNAL CURRENT LIMIT (X)
V
BG
+ V
T
V
BG
240 µA
400 µA
CONTROL Pin
MULTI-FUNCTION (M)
(Positive Current Sense - Under-Voltage,
Overvoltage, Maximum Duty
Cycle Reduction)
(Negative Current Sense - ON/OFF,
Current Limit Adjustment)
PI-2548-092399
TOPSwitch-GX
P and G Package
TOP242-250
15
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9/02
Figure 15. Half Frequency Standby Mode (For High Standby
Efficiency).
Figure 13. Full Frequency Operation (132 kHz). Figure 14. Half Frequency Operation (66 kHz).
Typical Uses of FREQUENCY (F) Pin
PI-2654-071700
DC
Input
Voltage
+
-
D
S
C
CONTROL
F
PI-2655-071700
DC
Input
Voltage
+
-
D
S
C
CONTROL
F
PI-2656-040501
DC
Input
Voltage
+
-
D
S
C
STANDBY
QS can be an optocoupler output.
CONTROL
F
20 k
RHF 1 nF
QS47 k
TOP242-250
16
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins
XF
PI-2617-050100
DC
Input
Voltage
+
-
DCS D
S
C
CONTROL
L
CLXSF D
PI-2618-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
2MR
LS
V
UV
= I
UV
x R
LS
V
OV
=
I
OV
x
R
LS
For R
LS
= 2 M
V
UV
= 100 VDC
V
OV
=
450 VDC
DC
MAX
@100 VDC = 78%
DC
MAX
@375 VDC = 38%
PI-2510-040501
DC
Input
Voltage
+
-
DM
S
C
V
UV
= R
LS
x I
UV
For Value Shown
V
UV
= 100 VDC
R
LS
6.2 V
2 M
22 k
CONTROL
PI-2620-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
2 M
30 k
R
LS
1N4148
V
OV
= I
OV
x
R
LS
For Values Shown
V
OV
= 450 VDC
X
PI-2623-040501
DC
Input
Voltage
+
-
D
S
C
R
IL
For R
IL
= 12 k
I
LIMIT
= 69%
See fig. 55 for other
resistor values (R
IL
)
For R
IL
= 25 k
I
LIMIT
= 43%
CONTROL
X
PI-2624-040501
DC
Input
Voltage
+
-
D
S
C
2.5 MR
LS
6 k
R
IL
100% @ 100 VDC
63% @ 300 VDC
I
LIMIT
=
I
LIMIT
=
CONTROL
Figure 16. Three Terminal Operation (LINE-SENSE and
EXTERNAL CURRENT LIMIT Features Disabled.
FREQUENCY Pin can be tied to SOURCE or
CONTROL Pin).
Figure 17. Line-Sensing for Under-Voltage, Overvoltage and
Line Feed Forward.
Figure 18. Line-Sensing for Under-Voltage Only (Overvoltage
Disabled). Figure 19. Line-Sensing for Overvoltage Only (Under-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.
TOP242-250
17
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9/02
Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)
Figure 22. Active-on (Fail Safe) Remote ON/OFF.
X
PI-2625-040501
DC
Input
Voltage
+
-
D
S
C
ON/OFF
47 k
Q
R
can be an optocoupler
output or can be replaced by
a manual switch.
Q
R
CONTROL
X
ON/OFF
47 k
PI-2626-040501
DC
Input
Voltage
+
-
D
S
C
RIL QR
12 k
For RIL =
ILIMIT = 69 %
25 k
For RIL =
ILIMIT = 43 %
QR can be an optocoupler
output or can be replaced
by a manual switch.
CONTROL
PI-2627-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
47 k
Q
R
R
MC
45 k
QR can be an
optocoupler output
or can be replaced
by a manual switch.
ON/OFF
X
R
IL
PI-2622-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
47 k
2 M
Q
R
R
LS
ON/OFF For RLS = 2 M
VUV = 100 VDC
VOV = 450 VDC
QR can be an optocoupler
output or can be replaced
by a manual switch.
X
ON/OFF
47 k
PI-2628-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
R
IL
R
LS
Q
R
2 M
V
UV
= I
UV
x R
LS
V
OV
=
I
OV
x
R
LS
DC
MAX
@100 VDC = 78%
DC
MAX
@375 VDC = 38%
12 k
For R
IL
=
I
LIMIT
= 69 %
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
Figure 23. Active-off Remote ON/OFF. Maximum Duty Cycle will
be reduced.
Figure 24. Active-on Remote ON/OFF with Externally Set Current
Limit. Figure 25. Active-off Remote ON/OFF with Externally Set Current
Limit.
Figure 26. Active-off Remote ON/OFF with LINE-SENSE. Figure 27. Active-on Remote ON/OFF with LINE-SENSE and
EXTERNAL CURRENT LIMIT.
PI-2621-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
47 k
Q
R
R
MC
45 k
QR can be an
optocoupler output or
can be replaced
by a manual switch.
ON/OFF
TOP242-250
18
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)
Figure 28. Line-Sensing and Externally Set Current Limit.
PI-2640-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
ON/OFF
47 k
Q
R
can be an optocoupler
output or can be replaced by
a manual switch.
300 k
Q
R
Figure 29. Active-on Remote ON/OFF.
X
PI-2629-040501
DC
Input
Voltage
+
-
D
S
C
CONTROL
L
R
IL
R
LS
12 k
2 M
V
UV
= I
UV
x R
LS
V
OV
=
I
OV
x
R
LS
For R
LS
= 2 M
DC
MAX
@100 VDC = 78%
DC
MAX
@375 VDC = 38%
For R
IL
= 12 k
I
LIMIT
= 69%
See fig. 55 for other
resistor values (R
IL
)
to select different I
LIMIT
values
V
UV
= 100 VDC
V
OV
= 450 VDC
TOP242-250
19
H
9/02
Figure 32. Line Sensing for Under-Voltage Only (Overvoltage
Disabled).
PI-2510-040501
DC
Input
Voltage
+
-
DM
S
C
VUV = RLS x IUV
For Value Shown
VUV = 100 VDC
R
LS
6.2 V
2 M
22 k
CONTROL
Figure 33. Line Sensing for Overvoltage Only (Under-Voltage
Disabled). Maximum Duty Cycle will be reduced at
Low Line.
Figure 34. Externally Set Current Limit.
PI-2517-040501
DC
Input
Voltage
+
-
DM
S
C
For RIL = 12 k
ILIMIT = 69%
CONTROL
RIL
See fig. 55 for other
resistor values (RIL)
For RIL = 25 k
ILIMIT = 43%
to select different
ILIMIT values
PI-2516-040501
DC
Input
Voltage
+
-
DM
S
C
VOV = IOV x RLS
For Values Shown
VOV = 450 VDC
CONTROL
R
LS
1N4148
2 M
30 k
Figure 30. Three Terminal Operation (MULTI-FUNCTION
Features Disabled).
PI-2508-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
M
C
DS
CD S
S
SS
M
PI-2509-040501
DC
Input
Voltage
+
-
DM
S
C
VUV = IUV x RLS
VOV = IOV x RLS
For RLS = 2 M
VUV = 100 VDC
VOV = 450 VDC
DCMAX@100 VDC = 78%
DCMAX@375 VDC = 38%
CONTROL
R
LS
2 M
Typical Uses of MULTI-FUNCTION (M) Pin
Figure 35. Current Limit Reduction with Line Voltage.
PI-2518-040501
DC
Input
Voltage
+
-
DM
S
C
CONTROL
RIL
RLS 2.5 M
6 k
100% @ 100 VDC
63% @ 300 VDC
ILIMIT =
ILIMIT =
Figure 31. Line Sensing for Undervoltage, Over-Voltage and
Line Feed Forward.
TOP242-250
20
H
9/02
General Information & Table of Contents
Product Selector Guide 1
Data Sheets 2
Application Notes 3
Design Ideas 4
Design Tools 5
Quality and Reliability 6
Package Information 7
DPA-Switch
DC-DC Seminar 8
LinkSwitch
&
TinySwitch-II
AC-DC Seminar 9
TOPSwitch-GX
AC-DC Seminar 10
Sales Representatives and Distributors 11
PI-2522-040501
DC
Input
Voltage
+
-
D
S
C
RMC
45 k
M
CONTROL
QR
QR can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 k
Figure 37. Active-off Remote ON/OFF. Maximum Duty Cycle will
be Reduced.
Figure 36. Active-on (Fail Safe) Remote ON/OFF.
PI-2519-040501
DC
Input
Voltage
+
-
D
S
C
Q
R
ON/OFF
M
CONTROL
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
47 k
PI-2523-040501
DC
Input
Voltage
+
-
D
S
C
R
LS
M For R
LS
= 2 M
V
UV
= 100 VDC
V
OV
= 450 VDC
CONTROL
Q
R
2 M
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 k
Figure 40. Active-off Remote ON/OFF with LINE-SENSE.
Figure 39. Active-off Remote ON/OFF with Externally Set
Current Limit.
PI-2521-040501
DC
Input
Voltage
+
-
D
S
C
R
IL
R
MC
24 k
12 k
M
CONTROL
Q
R
2R
IL
R
MC
=
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 k
Figure 38. Active-on Remote ON/OFF with Externally Set
Current Limit.
PI-2520-040501
DC
Input
Voltage
+
-
D
S
C
Q
R
R
IL
M
CONTROL
12 k
For R
IL
=
I
LIMIT
= 69 %
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 k
25 k
For R
IL
=
I
LIMIT
= 43 %
Typical Uses of MULTI-FUNCTION (M) Pin (cont.)
TOP242-250
21
H
9/02
Figure 41. 30 W Power Supply using External Current Limit Programming and Line Sensing for UV and OV.
Application Examples
A High Efficiency, 30 W, Universal Input Power Supply
The circuit shown in Figure 41 takes advantage of several of
the TOPSwitch-GX features to reduce system cost and power
supply size and to improve efficiency. This design delivers
30 W at 12 V, from an 85 to 265 VAC input, at an ambient of
50 °C, in an open frame configuration. A nominal efficiency
of 80% at full load is achieved using TOP244Y.
The current limit is externally set by resistors R1 and R2 to a
value just above the low line operating peak DRAIN current
of approximately 70% of the default current limit. This allows
use of a smaller transformer core size and/or higher transformer
primary inductance for a given output power, reducing
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 line
voltage. This function in combination with the built-in 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 extended maximum duty cycle feature of
TOPSwitch-GX (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 a 60 V Schottky rectifier can be used
for up to 15 V outputs, which greatly improves power supply
efficiency. The frequency 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.
12 V
@ 2.5 A
D2
1N4148
T1
C5
47 µF
10 V
U2
LTV817A
VR2
1N5240C
10 V, 2%
R6
150
R15
150
C14
1 nF
D1
UF4005
R3
68 k
2 W
C3
4.7 nF
1 kV
CY1
2.2 nF
U1
TOP244Y
DL
SXF
C
R8
150
C1
68 µF
400 V
C6
0.1 µF
D8
MBR1060 C10
560 µF
35 V
C12
220 µF
35 V
C11
560 µF
35 V RTN
R5
6.8
R1
4.7 M
1/2 W
R4
2 M
1/2 W
R2
9.09 k
PI-2657-040501
L3
3.3 µH
BR1
600 V
2A
F1
3.15 A
J1
L1
20 mH
L
N
CX1
100 nF
250 VAC
CONTROL
CONTROL
TOPSwitch-GX
PERFORMANCE SUMMARY
Output Power: 30 W
Regulation: ± 4%
Efficiency: 79%
Ripple: 50 mV pk-pk
85-265 VAC