Power integrations TOP252GN, TOP253GN, TOP252PN, TOP253PN, TOP253MN Series Manual

TOP252-262
TOPSwitch-HX Family

Enhanced EcoSmart, Integrated Off-Line Switcher with
Advanced Feature Set and Extended Power Range

Product Highlights

Lower System Cost, Higher Design Flexibility

• Multi-mode operation maximizes efficiency at all loads

• New eSIP-7F and eSIP-7C packages

• Low thermal impedance junction-to-case (2 °C per watt)

• Low height is ideal for adapters where space is limited

• Simple mounting using a clip to aid low cost manufacturing

• Horizontal eSIP-7F package ideal for ultra low height adapter

and monitor applications

• Extended package creepage distance from DRAIN pin to

adjacent pin and to heat sink

• No heat sink required up to 35 W using P, G and M packages

with universal input voltage and up to 48 W at 230 VAC

• Output overvoltage protection (OVP) is user programmable for

latching/non-latching shutdown with fast AC reset

• Allows both primary and secondary sensing

• Line undervoltage (UV) detection prevents turn-off glitches

• Line overvoltage (OV) shutdown extends line surge limit

• Accurate programmable current limit

• Optimized line feed-forward for line ripple rejection

• 132 kHz frequency (254Y-258Y and all E/L packages) reduces

transformer and power supply size

• Half frequency option for video applications

• Frequency jittering reduces EMI filter cost

AC

IN

D

TOPSwitch-HX

S

Figure 1. Typical Flyback Application.

• Heat sink is connected to SOURCE for low EMI

• Improved auto-restart delivers <3% of maximum power in

V

CONTROL

C

FX

PI-4510-100206

DC

OUT

+

-

short circuit and open loop fault conditions

• Accurate hysteretic thermal shutdown function automatically

recovers without requiring a reset

• Fully integrated soft-start for minimum start-up stress

• Extended creepage between DRAIN and all other pins

improves field reliability

Output Power Table

Product

5

TOP252PN/GN

TOP252MN 21 W 13 W

TOP253PN/GN

TOP253MN 43 W 29 W

TOP254PN/GN

TOP254MN 62 W 40 W

TOP255PN/GN

TOP255MN 81 W 52 W

TOP256PN/GN

TOP256MN 98 W 64 W

TOP257PN/GN

TOP257MN 119 W 78 W

TOP258PN/GN

TOP258MN 140 W 92 W

Table 1. Output Power Table. (for notes see page 2).

230 VAC ±15%

Adapter

1

Frame

9 W 15 W

15 W 25 W

16 W 28 W

19 W 30 W

21 W 34 W

25 W 41 W

29 W 48 W

Open

4

Peak3Adapter

2

21 W

38 W

47 W

54 W

63 W

70 W

77 W

85-265 VAC

Open

1

Frame

6 W 10 W

9 W 15 W

11 W 20 W

13 W 22 W

15 W 26 W

19 W 30 W

22 W 35 W

Peak

2

13 W

25 W

30 W

35 W

40 W

45 W

50 W

3

Product

5

230 VAC ±15% 85-265 VAC

Open

Adapter

1

Frame

Adapter

2

1

TOP252EN/EG 10 W 21 W 6 W 13 W
TOP253EN/EG 21 W 43 W 13 W 29 W
TOP254EN/YN/EG 30 W 62 W 20 W 43 W
TOP255EN/YN/EG 40 W 81 W 26 W 57 W
TOP255LN 40 W 81 W 26 W 57 W

TOP256EN/YN/EG 60 W 119 W 40 W 86 W

TOP256LN 60 W 88 W 40 W 64 W
TOP257EN/YN/EG 85 W 157 W 55 W 119 W
TOP257LN 85 W 105 W 55 W 78 W
TOP258EN/YN/EG 105 W 195 W 70 W 148 W
TOP258LN 105 W 122 W 70 W 92 W

TOP259EN/YN/EG 128 W 238 W 80 W 171 W

TOP259LN 128 W 162 W 80 W 120 W
TOP260EN/YN/EG 147 W 275 W 93 W 200 W
TOP260LN 147 W 190 W 93 W 140 W
TOP261EN/YN/EG 177 W 333 W 118 W 254 W
TOP261LN 177 W 244 W 118 W 177 W
TOP262EN
TOP262LN

6

6

177 W 333 W 118 W 254 W
177 W 244 W 118 W 177 W

Open

Frame

2

www.power.com August 2016

This Product is Covered by Patents and/or Pending Patent Applications.

TOP252-262

EcoSmart™– Energy Efficient

• Energy efficient over entire load range

• No-load consumption

• Less than 200 mW at 230 VAC

• Standby power for 1 W input

• >600 mW output at 110 VAC input

• >500 mW output at 265 VAC input

Description

TOPSwitch™-HX cost effectively incorporates a 700 V power
MOSFET, high voltage switched current source, PWM control,
oscillator, thermal shutdown circuit, fault protection and other
control circuitry onto a monolithic device.

Notes for Table 1:

1. Minimum continuous power in a typical non-ventilated
enclosed adapter measured at +50 °C ambient. Use of an
external heat sink will increase power capability.

2. Minimum continuous power in an open frame design at
+50 °C ambient.

3. Peak power capability in any design at +50 °C ambient.

4. 230 VAC or 110/115 VAC with doubler.

5. Packages: P: DIP-8C, G: SMD-8C, M: SDIP-10C,
Y: TO-220-7C, E: eSIP-7C, L: eSIP-7F.
See part ordering information.

6. TOP261 and TOP262 have the same current limit set point. In
some applications TOP262 may run cooler than TOP261 due
to a lower R

for the larger device.

DS(ON)

Y Package Option for TOP259-261

In order to improve noise-immunity on large TOPSwitch-HX
Y package parts, the F pin has been removed (TOP259-261YN
are fixed at 66 kHz switching frequency) and replaced with a
SIGNAL GROUND (G) pin. This pin acts as a low noise path for
the C pin capacitor and the X pin resistor. It is only required for
the TOP259-261YN package parts.

AC

IN

D

TOPSwitch-HX

S

Figure 2. Typical Flyback Application TOP259YN, TOP260YN and TOP261YN.

V

CONTROL

C

GX

PI-4973-122607

DC

OUT

+

-

2

Rev. J 08/16

www.power.com

TOP252-262

Section List

Functional Block Diagram ....................................................................................................................................... 4

Pin Functional Description ...................................................................................................................................... 6

TOPSwitch-HX Family Functional Description ....................................................................................................... 7

CONTROL (C) Pin Operation .................................................................................................................................... 8

Oscillator and Switching Frequency .......................................................................................................................... 8

Pulse Width Modulator ............................................................................................................................................ 9

Maximum Load Cycle .............................................................................................................................................. 9

Error Amplifier .......................................................................................................................................................... 9

On-Chip Current Limit with External Programmability ............................................................................................... 9

Line Undervoltage Detection (UV) ........................................................................................................................... 10

Line Overvoltage Shutdown (OV) ............................................................................................................................ 11

Hysteretic or Latching Output Overvoltage Protection (OVP)...................................................................................11

Line Feed-Forward with DC

Remote ON/OFF and Synchronization .................................................................................................................... 13

Soft-Start ............................................................................................................................................................... 13

Shutdown/Auto-Restart ......................................................................................................................................... 13

Hysteretic Over-Temperature Protection ................................................................................................................. 13

Bandgap Reference ............................................................................................................................................... 13

High-Voltage Bias Current Source .......................................................................................................................... 13

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

Typical Uses of VOLTAGE MONITOR (V) and EXTERNAL CURRENT LIMIT (X) Pins .......................................... 16

Typical Uses of MULTI-FUNCTION (M) Pin ........................................................................................................... 18

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

A High Efficiency, 35 W, Dual Output – Universal Input Power Supply ..................................................................... 21

A High Efficiency, 150 W, 250-380 VDC Input Power Supply .................................................................................. 22

A High Efficiency, 20 W Continuous – 80 W Peak, Universal Input Power Supply ................................................... 23

A High Efficiency, 65 W, Universal Input Power Supply ........................................................................................... 24

Key Application Considerations .............................................................................................................................. 25

TOPSwitch-HX vs.TOPSwitch-GX

TOPSwitch-HX Design Considerations .................................................................................................................. 26

TOPSwitch-HX Layout Considerations ................................................................................................................... 27

Quick Design Checklist .......................................................................................................................................... 31

Design Tools .......................................................................................................................................................... 31

Product Specifications and Test Conditions .......................................................................................................... 32

Typical Performance Characteristics .................................................................................................................... 39

Package Outlines .................................................................................................................................................... 43

Part Ordering Information ........................................................................................................................................ 47

Reduction .............................................................................................................. 13

MAX

.......................................................................................................................

. 25

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3

Rev. J 08/16

TOP252-262

SOURCE (S)

SOURCE (S)

CONTROL (C)

MULTI-

FUNCTION (M)

Z

C

SHUNT REGULATOR/

ERROR AMPLIFIER

I

FB

CURRENT

LIMIT

ADJUST

LINE

SENSE

V

C

0

INTERNAL
SUPPLY

1

DRAIN (D)

-

+

-

5.8 V

+

V

I (LIMIT)

ON/OFF

+ V

V

BG

T

5.8 V

4.8 V

INTERNAL UV

COMPARATOR

-

STOP LOGIC

DC

MAX

STOP

OSCILLATOR

WITH JITTER

OV/

OVPV

UV

DC

MAX

F REDUCTION

SOFT

START

SOFT START

D

MAX

CLOCK

÷ 16

SHUTDOWN/

AUTO-RESTART

HYSTERETIC

THERMAL

SHUTDOWN

SRQ

K

PS(UPPER)

K

PS(LOWER)

CURRENT LIMIT

COMPARATOR

+

-

+

-

+

SOURCE (S)

CONTROLLED

TURN-ON

GATE DRIVER

LEADING

EDGE

BLANKING

F REDUCTION

SOFT START
I

K

PS(UPPER)

K

PS(LOWER)

FB

I

PS(UPPER)

I

PS(LOWER)

PWM

OFF

Figure 3a. Functional Block Diagram (P and G Packages).

CONTROL (C)

EXTERNAL

CURRENT

LIMIT (X)

VOLTAGE

MONITOR (V)

Z

C

SHUNT REGULATOR/

ERROR AMPLIFIER

I

FB

-

+

CURRENT

LIMIT

ADJUST

V

1 V

LINE

SENSE

V

C

5.8 V

5.8 V

V

I (LIMIT)

ON/OFF

+ V

BG

T

4.8 V

STOP LOGIC

OV/

OVPV

UV

DC

MAX

I

PS(UPPER)

I

PS(LOWER)

+

-

INTERNAL UV

COMPARATOR

STOP

OSCILLATOR

DC

MAX

WITH JITTER

F REDUCTION

F REDUCTION

SOFT START
I

FB

I

PS(UPPER)

I

PS(LOWER)

PWM

SOFT

START

SOFT START

D

MAX

CLOCK

OFF

0

1

÷ 16

SHUTDOWN/

AUTO-RESTART

HYSTERETIC

THERMAL

SHUTDOWN

INTERNAL
SUPPLY

SRQ

I

PS(UPPER)

I

PS(LOWER)

CURRENT LIMIT

COMPARATOR

CONTROLLED

TURN-ON

GATE DRIVER

PI-4508-120307

-

+

-

+

-

+

SOURCE (S)

LEADING

EDGE

BLANKING

DRAIN (D)

Figure 3b. Functional Block Diagram (M Package).

4

Rev. J 08/16

PI-4643-040507

www.power.com

TOP252-262

SOURCE (S)

GROUND (G)

SOURCE (S)

CONTROL (C)

EXTERNAL CURRENT

LIMIT (X)

VOLTAGE

MONITOR (V)

FREQUENCY (F)

V

Z

C

SHUNT REGULATOR/

ERROR AMPLIFIER

-

+

I

FB

CURRENT

LIMIT

ADJUST

V

BG

1 V

LINE

SENSE

C

+ V

OVPV

5.8 V

V

I (LIMIT)

ON/OFF

T

DC

OV/

UV

MAX

K

PS(UPPER)

K

PS(LOWER)

5.8 V

4.8 V

INTERNAL UV

COMPARATOR

STOP LOGIC

DC

66k/132k

SOFT START
I

FB

I

PS(UPPER)

I

PS(LOWER)

+

-

MAX

F REDUCTION

F REDUCTION

SOFT

STOP

START

OSCILLATOR
WITH JITTER

PWM

SOFT START

D

MAX

CLOCK

OFF

0

1

÷ 16

SHUTDOWN/

AUTO-RESTART

HYSTERETIC

THERMAL

SHUTDOWN

INTERNAL
SUPPLY

SRQ

K

PS(UPPER)

K

PS(LOWER)

CURRENT LIMIT

COMPARATOR

CONTROLLED

TURN-ON

GATE DRIVER

-

+

-

+

-

+

SOURCE (S)

LEADING

EDGE

BLANKING

DRAIN (D)

Figure 3c. Functional Block Diagram (TOP254-258 YN Package and all eSIP Packages).

CONTROL (C)

EXTERNAL
CURRENT

LIMIT (X)

VOLTAGE

MONITOR (V)

Z

C

SHUNT REGULATOR/

ERROR AMPLIFIER

I

FB

-

+

CURRENT

LIMIT

ADJUST

V

1 V

LINE

SENSE

V

C

+

5.8 V

-

5.8 V

V

I (LIMIT)

ON/OFF

+ V

BG

T

4.8 V

INTERNAL UV

COMPARATOR

SOFT START

STOP LOGIC

SOFT

DC

MAX

STOP

START

OSCILLATOR
WITH JITTER

D

MAX

CLOCK

OV/

OVPV

UV

DC

MAX

F REDUCTION

F REDUCTION

SOFT START

K

PS(UPPER)

K

PS(LOWER)

I

FB

I

PS(UPPER)

I

PS(LOWER)

PWM

OFF

0

1

÷ 16

SHUTDOWN/

AUTO-RESTART

HYSTERETIC

THERMAL

SHUTDOWN

INTERNAL
SUPPLY

SRQ

K

PS(UPPER)

K

PS(LOWER)

CURRENT LIMIT

COMPARATOR

CONTROLLED

GATE DRIVER

-

+

-

+

-

+

SOURCE (S)

TURN-ON

LEADING

BLANKING

PI-4511-012810

DRAIN (D)

EDGE

Figure 3d. Functional Block Diagram TOP259YN, TOP260YN, TOP261YN.

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PI-4974-122607

SIGNAL

5

Rev. J 08/16

TOP252-262

Pin Functional Description

DRAIN (D) Pin:

High-voltage power MOSFET DRAIN pin. The internal start-up
bias current is drawn from this pin through a switched high­voltage 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 internal
bias current during normal operation. It is also used as the
connection point for the supply bypass and auto-restart/
compensation capacitor.

EXTERNAL CURRENT LIMIT (X) Pin (Y, M, E and L package):

Input pin for external current limit adjustment and remote
ON/OFF. A connection to SOURCE pin disables all functions on
this pin.

E Package (eSIP-7C)

Exposed Pad
(Hidden)
Internally
Connected to
SOURCE Pin

Y Package (TO-220-7C)

Note: Y package for TOP259-261

VOLTAGE MONITOR (V) Pin (Y & M package only):

Input for OV, UV, line feed forward with DC

reduction, output

MAX

overvoltage protection (OVP), remote ON/OFF and device reset.
A connection to the SOURCE pin disables all functions on this pin.

MULTI-FUNCTION (M) Pin (P & G packages only):

This pin combines the functions of the VOLTAGE MONITOR (V)
and EXTERNAL CURRENT LIMIT (X) pins of the Y package into
one pin. Input pin for OV, UV, line feed forward with DC

V

X

R

12 kΩ

VUV = IUV × R
V

=

OV

For R

4 MΩ

VUV = 102.8 VDC
V

DC

MAX

DC

MAX

C

For RIL = 12 kΩ

I

See Figure 55b for

IL

other resistor values
(R
I

LS + VV

I

R

×

OV

LS + VV

= 4 MΩ

LS

= 451 VDC

OV

@100 VDC = 76%
@375 VDC = 41%

= 61%

LIMIT

) to select different

IL

values.

LIMIT

+

R

LS

DC

Input

Voltage

D

CONTROL

S

-

Figure 5. TOP254-258 Y and All M/E/L Package Line Sense and Externally Set

Current Limit.

MAX

(IV = IUV)

(IV = IOV)

PI-4711-021308

V

7D5S4F3C2X1

L Package (eSIP-7F)

Lead Bend
Outward from Drawing
(Refer to eSIP-7F Package

7D5S4F3C2X1

V

Outline Drawing)

M Package

V

1

2

X

3

C

5

D

10

S

9

S

S

8

S

7

6

S

P and G Package

M

1

C

2

4

D

Figure 4. Pin Configuration (Top View).

S

8

7

S

6

S

S

5

Tab Internally
Connected to
SOURCE Pin

V

Y Package (TO-220-7C)

Note: Y package for TOP254-258

Tab Internally
Connected to
SOURCE Pin

V

7D5G4S3C2X1

7D5F4S3C2X1

PI-4644-091108

4 MΩ

V

X G

VUV = IUV × R
V

I

=

×

OV

OV

= 4 MΩ

For R

LS

VUV = 102.8 VDC

= 451 VDC

V

OV

DC

@100 VDC = 76%

MAX

@375 VDC = 41%

DC

MAX

C

For RIL = 12 kΩ

I

LIMIT

See Figure 55b for
other resistor values

) to select different

(R

IL

values.

I

LIMIT

+

R

LS

DC

Input

Voltage

-

Figure 6. TOP259-261 Y Package Line Sense and External Current Limit.

D

S

CONTROL

R

IL

12 kΩ

LS + VV

R

LS + VV

= 61%

(IV = IUV)

(IV = IOV)

+

DC

Input

Voltage

D M

-

Figure 7. P/G Package Line Sense.

S

R

LS

CONTROL

4 MΩ

VUV = IUV × R
V

I

=

×

OV

OV

= 4 MΩ

For R

LS

= 102.8 VDC

V

UV

V

DC
DC

C

451 VDC

=

OV

@100 VDC = 76%

MAX

@375 VDC = 41%

MAX

LS + VM

R

LS + VM

PI-4712-120307

(IM = IUV)
(IM = IOV)

PI-4983-021308

6

Rev. J 08/16

www.power.com

+

DC

Input

Voltage

D M

R

IL

-

Figure 8. P/G Package Externally Set Current Limit.

CONTROL

S

C

For R

= 12 kΩ

IL

= 61%

I

LIMIT

For R

= 19 kΩ

IL

= 37%

I

LIMIT

See Figure 55b for other
resistor values (R
select different I

) to

IL

values.

LIMIT

PI-4713-021308

Auto-Restart

78

Duty Cycle (%) Drain Peak Current

100

TOP252-262

Slope = PWM Gain

(constant over load range)

CONTROL

Current

reduction, output overvoltage protection (OVP), external current
limit adjustment, remote ON/OFF and device reset. A
connection to SOURCE pin disables all functions on this pin
and makes TOPSwitch-HX operate in simple three terminal
mode (like TOPSwitch-II).

FREQUENCY (F) Pin (TOP254-258Y, and all E and L packages):

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 66 kHz
operation in the P, G, M package and TOP259YN, TOP260YN
an d TO P261YN.

SIGNAL GROUND (G) Pin (TOP259YN, TOP260YN &
TOP261YN only):

Return for C pin capacitor and X pin resistor.

SOURCE (S) Pin:

Output MOSFET source connection for high voltage power
return. Primary side control circuit common and reference point.

TOPSwitch-HX Family Functional Description

Like TOPSwitch-GX, TOPSwitch-HX 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 9.

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 and thermal
shutdown, the TOPSwitch-HX 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, VOLTAGE-MONITOR, and
EXTERNAL CURRENT LIMIT (available in Y and E/L packages),

55

25

To Current Limit Ratio (%)

CONTROL

Current

Full Frequency Mode

132

Variable

Frequency

66

Jitter

Frequency (kHz)

30

IB I

CD1

Figure 9. Control Pin Characteristics (Multi-Mode Operation).

I

C01

Mode

I

C02

I

C03

I

Low

Frequency

Mode

Multi-Cycle
Modulation

CONTROL

COFF

Current

PI-4645-041107

two terminals, VOLTAGE-MONITOR and EXTERNAL CURRENT
LIMIT (available in M package) or one terminal MULTI-FUNCTION
(available in P and G package) have been used to implement
some of the new functions. These terminals can be connected
to the SOURCE pin to operate the TOPSwitch-HX in a
TOPSwitch-like three terminal mode. However, even in this three
terminal mode, the TOPSwitch-HX offers many transparent
features that do not require any external components:

1. A fully integrated 17 ms soft-start significantly reduces or
eliminates output overshoot in most applications by sweeping
both current limit and frequency from low to high to limit the
peak currents and voltages during start-up.

2. A maximum duty cycle (DC

) of 78% allows smaller input

MAX

storage capacitor, lower input voltage requirement and/or
higher power capability.

3. Multi-mode operation optimizes and improves the power
supply efficiency over the entire load range while maintaining
good cross regulation in multi-output supplies.

www.power.com

7

Rev. J 08/16

TOP252-262

4. Switching frequency of 132 kHz reduces the transformer size
with no noticeable impact on EMI.

5. Frequency jittering reduces EMI in the full frequency mode at
high load condition.

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. Reduction of the auto-restart duty cycle and frequency to
improve the protection of the power supply and load during
open loop fault, short circuit, or loss of regulation.

9. Tighter tolerances on I2f power coefficient, current limit
reduction, PWM gain and thermal shutdown threshold.

The VOLTAGE-MONITOR (V) pin is usually used for line sensing
by connecting a 4 MW resistor from this pin to the rectified DC
high voltage bus to implement line overvoltage (OV), under­voltage (UV) and dual-slope line feed-forward with DC

MAX

reduction. In this mode, the value of the resistor determines the
OV/UV thresholds and the DC

is reduced linearly with a dual

MAX

slope to improve line ripple rejection. In addition, it also
provides another threshold to implement the latched and
hysteretic output overvoltage protection (OVP). The pin can
also be used as a remote ON/OFF using the I

threshold.

UV

The EXTERNAL CURRENT LIMIT (X) pin can be used to reduce
the current limit externally to a value close to the operating peak
current, by connecting the pin to SOURCE through a resistor.
This pin can also be used as a remote ON/OFF input.

For the P and G package the VOLTAGE-MONITOR and
EXTERNAL CURRENT LIMIT pin functions are combined on
one MULTI-FUNCTION (M) pin. However, some of the functions
become mutually exclusive.

The FREQUENCY (F) pin in the TOP254-258 Y and E/L packages
set the switching frequency in the full frequency PWM mode 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 the CONTROL pin instead. Leaving this pin open is
not recommended. In the P, G and M packages and the
TOP259-261 Y packages, the frequency is set internally at
66 kHz in the full frequency PWM mode.

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
feedback signal from the supply current. CONTROL pin voltage
V

is the supply voltage for the control circuitry including the

C

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 V

reaches

C

approximately 5.8 V, the control circuitry is activated and the
soft-start begins. The soft-start circuit gradually increases the
drain peak current and switching frequency from a low starting
value to the maximum drain peak current at the full frequency
over approximately 17 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 undervoltage lockout
threshold). When the externally fed current charges the
CONTROL pin to the shunt regulator voltage of 5.8 V, current in
excess of the consumption of the chip is shunted to SOURCE
through an NMOS current mirror as shown in Figure 3. The
output current of that NMOS current mirror controls the duty
cycle of the power MOSFET to provide closed loop regulation.
The shunt regulator has a finite low output impedance Z

that

C

sets the gain of the error amplifier when used in a primary
feedback configuration. The dynamic impedance Z

of the

C

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 undervoltage comparator keeps V

within a window of

C

typically 4.8 V to 5.8 V by turning the high-voltage current
source on and off as shown in Figure 11. The auto-restart
circuit has a divide-by-sixteen counter, which prevents the
output MOSFET from turning on again until sixteen discharge/
charge cycles have elapsed. This is accomplished by enabling
the output MOSFET only when the divide-by-sixteen counter
reaches the full count (S15). The counter effectively limits
TOPSwitch-HX power dissipation by reducing the auto-restart
duty cycle to typically 2%. 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
triangular waveform for the timing of the pulse width modulator.
This oscillator sets the pulse width modulator/current limit latch
at the beginning of each cycle.

The nominal full 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 TOP254-258 Y and E, L packages), when shorted to the
CONTROL pin, lowers the full switching frequency to 66 kHz

8

Rev. J 08/16

www.power.com

TOP252-262

PI-4530-041107

f

+

Switching

Frequency

V

DRAIN

Figure 10. Switching Frequency Jitter (Idealized V

OSC

f

-

OSC

4 ms

Time

Waveforms).

DRAIN

(half frequency), which may be preferable in some cases such
as noise sensitive video applications or a high efficiency
standby mode. Otherwise, the FREQUENCY pin should be
connected to the SOURCE pin for the default 132 kHz. In the
M, P and G packages and the TOP259-261 Y package option,
the full frequency PWM mode is set at 66 kHz, for higher
efficiency and increased output power in all applications.

To further reduce the EMI level, the switching frequency in the
full frequency PWM mode is jittered (frequency modulated) by
approximately ±2.5 kHz for 66 kHz operation or ±5 kHz for
132 kHz operation at a 250 Hz (typical) rate as shown in
Figure 10. The jitter is turned off gradually as the system is
entering the variable frequency mode with a fixed peak drain
current.

Pulse Width Modulator

The pulse width modulator implements multi-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 9).
The feedback error signal, in the form of the excess current, 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.

To optimize power supply efficiency, four different control
modes are implemented. At maximum load, the modulator
operates in full frequency PWM mode; as load decreases, the
modulator automatically transitions, first to variable frequency
PWM mode, then to low frequency PWM mode. At light load,
the control operation switches from PWM control to multi-cycle­modulation control, and the modulator operates in multi-cycle­modulation mode. Although different modes operate differently
to make transitions between modes smooth, the simple
relationship between duty cycle and excess CONTROL pin
current shown in Figure 9 is maintained through all three PWM
modes. Please see the following sections for the details of the
operation of each mode and the transitions between modes.

Full Frequency PWM mode: The PWM modulator enters full
frequency PWM mode when the CONTROL pin current (I
reaches I
kept constant at f

. In this mode, the average switching frequency is

B

(66 kHz for P, G and M packages and

OSC

C

)

TOP259-261 Y, pin selectable 132 kHz or 66 kHz for Y and E/L

packages). Duty cycle is reduced from DC
reduction of the on-time when I

is increased beyond IB. This

C

through the

MAX

operation is identical to the PWM control of all other TOPSwitch
families. TOPSwitch-HX only operates in this mode if the
cycle-by-cycle peak drain current stays above k
where k

is 55% (typical) and I

PS(UPPER)

(set) is the current limit

LIMIT

PS(UPPER)*ILIMIT

(set),

externally set via the X or M pin.

Variable Frequency PWM mode: When peak drain current is
lowered to k

PS(UPPER)

* I

(set) as a result of power supply load

LIMIT

reduction, the PWM modulator initiates the transition to variable
frequency PWM mode, and gradually turns off frequency jitter.
In this mode, peak drain current is held constant at k
I

(set) while switching frequency drops from the initial full

LIMIT

frequency of f
frequency of f

(132 kHz or 66 kHz) towards the minimum

OSC

(30 kHz typical). Duty cycle reduction is

MCM(MIN)

PS(UPPER)

*

accomplished by extending the off-time.

Low Frequency PWM mode: When switching frequency
reaches f

(30 kHz typical), the PWM modulator starts to

MCM(MIN)

transition to low frequency mode. In this mode, switching
frequency is held constant at f

and duty cycle is reduced,

MCM(MIN)

similar to the full frequency PWM mode, through the reduction
of the on-time. Peak drain current decreases from the initial
value of k
k

PS(LOW ER)*ILIMIT

* I

PS(UPPER)

(set), where k

(set) towards the minimum value of

LIMIT

is 25% (typical) and I

PS(LOW ER)

LIMIT

(set) is

the current limit externally set via the X or M pin.

Multi-Cycle-Modulation mode: When peak drain current is
lowered to k

PS(LOW ER)*ILIMIT

(set), the modulator transitions to
multi-cycle-modulation mode. In this mode, at each turn-on,
the modulator enables output switching for a period of T
at the switching frequency of f
at 30 kHz) with the peak drain current of k

(4 or 5 consecutive pulses

MCM(MIN)

PS(LOW ER)*ILIMIT

stays off until the CONTROL pin current falls below I

MCM(MIN)

(set), and

. This

C(OFF)

mode of operation not only keeps peak drain current low but
also minimizes harmonic frequencies between 6 kHz and
30 kHz. By avoiding transformer resonant frequency this way,
all potential transformer audible noises are greatly suppressed.

Maximum Duty Cycle

The maximum duty cycle, DC

, is set at a default maximum

MAX

value of 78% (typical). However, by connecting the VOLTAGE­MONITOR or MULTI-FUNCTION pin (depending on the
package) to the rectified DC high voltage bus through a resistor
with appropriate value (4 MW typical), the maximum duty cycle
can be made to decrease from 78% to 40% (typical) when input
line voltage increases from 88 V to 380 V, with dual gain slopes.

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 temperature­compensated bandgap reference. The CONTROL pin dynamic
impedance Z
CONTROL pin clamps external circuit signals to the V

sets the gain of the error amplifier. The

C

voltage

C

level. The CONTROL pin current in excess of the supply current
is separated by the shunt regulator and becomes the feedback
current I

for the pulse width modulator.

fb

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9

Rev. J 08/16

TOP252-262

V

V

LINE

0 V

~

~

~

UV

~

~

~

~

~

~

~

S14

S15

V

C

0 V

V

DRAIN

0 V

V

OUT

0 V

1

Note: S0 through S15 are the output states of the auto-restart counter

Figure 11. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-Restart (4) Power Down.

2

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 V
current causes V

with a threshold voltage. High drain

DS(ON)

to exceed the threshold voltage and turns

DS(ON)

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 R
The default current limit of TOPSwitch-HX is preset internally.

S13 S12 S0 S15 S13 S12 S0 S15S14

~

~

~

~

~

~

of the output MOSFET.

DS(ON)

~

~

~

~

~

~

3

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. This is due to dynamic characteristics of
the MOSFET. During startup and fault conditions the controller
prevents excessive drain currents by reducing the switching
frequency.

However, with a resistor connected between EXTERNAL
CURRENT LIMIT (X) pin (Y, E/L and M packages) or MULTI­FUNCTION (M) pin (P and G package) and SOURCE pin (for
TOP259-261 Y, the X pin is connected to the SIGNAL GROUND
(G) pin), current limit can be programmed externally to a lower
level between 30% and 100% of the default current limit. By
setting current limit low, a larger TOPSwitch-HX than necessary
for the power required can be used to take advantage of the
lower R

for higher efficiency/smaller heat sinking

DS(ON)

requirements. TOPSwitch-HX current limit reduction initial
tolerance through the X pin (or M pin) has been improved
significantly compare with previous TOPSwitch-GX. With a
second resistor connected between the EXTERNAL CURRENT
LIMIT (X) pin (Y, E/L and M packages) or MULTI-FUNCTION (M)
pin (P and 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.

Line Undervoltage Detection (UV)

At power up, UV keeps TOPSwitch-HX off until the input line
voltage reaches the undervoltage threshold. At power down,
UV prevents auto-restart attempts after the output goes out of
regulation. This eliminates power down glitches caused by slow
discharge of the large input storage capacitor present in
applications such as standby supplies. A single resistor
connected from the VOLTAGE-MONITOR pin (Y, E/L and M
packages) or MULTI-FUNCTION pin (P and G packages) 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 44% 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 (S15), the UV comparator is enabled. If the
UV high threshold is not exceeded, the MOSFET will be
disabled during the next cycle (see Figure 11). The UV feature

The leading edge blanking circuit inhibits the current limit

can be disabled independent of the OV feature.

comparator for a short time after the output MOSFET is turned

S14

2

S13

S12

~

~

~

~

~

~

4

S0 S15

S15

5.8 V

4.8 V

PI-4531-121206

10

Rev. J 08/16

www.power.com

TOP252-262

Line Overvoltage Shutdown (OV)

The same resistor used for UV also sets an overvoltage
threshold, which, once exceeded, will force TOPSwitch-HX to
stop switching instantaneously (after completion of the current
switching cycle). If this condition lasts for at least 100 ms, the
TOPSwitch-HX output will be forced into off state. Unlike with
TOPSwitch-GX, however, when the line voltage is back to

clamp network, bias winding return or power traces from other
converters. If the line sensing features are used, then the sense
resistors must be placed within 10 mm of the V-pin to minimize
the V-pin node area. The DC bus should then be routed to the
line sense resistors. Note that external capacitance must not
be connected to the V-pin as this may cause misoperation of
the V pin related functions.

normal with a small amount of hysteresis provided on the OV
threshold to prevent noise triggering, the state machine sets to
S13 and forces TOPSwitch-HX to go through the entire auto­restart sequence before attempting to switch again. The ratio
of OV and UV thresholds is preset at 4.5, as can be seen in
Figure 12. 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. The OV feature can be
disabled independent of the UV feature.

Hysteretic or Latching Output Overvoltage Protection (OVP)

The detection of the hysteretic or latching output overvoltage
protection (OVP) is through the trigger of the line overvoltage
threshold. The V-pin or M-pin voltage will drop by 0.5 V, and
the controller measures the external attached impedance
immediately after this voltage drops. If I

or IM exceeds I

V

OV(LS)

(336 mA typical) longer than 100 ms, TOPSwitch-HX will latch
into a permanent off state for the latching OVP. It only can be
reset if V
up-reset threshold (V

or VM goes below 1 V or VC goes below the power-

V

) and then back to normal.

C(RESET )

In order to reduce the no-load input power of TOPSwitch-HX
designs, the V-pin (or M-pin for P Package) operates at very low
currents. This requires careful layout considerations when
designing the PCB to avoid noise coupling. Traces and
components connected to the V-pin should not be adjacent to
any traces carrying switching currents. These include the drain,

or IM does not exceed I

V

100 ms, TOPSwitch-HX will initiate the line overvoltage and the
hysteretic OVP. Their behavior will be identical to the line
overvoltage shutdown (OV) that has been described in detail in
the previous section.

or exceeds no longer than

OV(LS)

If I

Voltage Monitor and External Current Limit Pin Table*

Figure Number 16 17 18 19 20 21 22 23 24 25 26 27 28

Three Terminal Operation

Line Undervoltage

Line Overvoltage

Line Feed-Forward (DC

Output Overvoltage Protection

Overload Power Limiting

External Current Limit

Remote ON/OFF

Device Reset

*This table is only a partial list of many VOLTAGE MONITOR and EXTERNAL CURRENT LIMIT Pin Configurations that are possible.

MAX

)

3

3 3 3 3 3 3

3 3 3 3 3 3

3 3 3 3 3

3 3

3

3 3 3 3 3

3 3 3

3

Table 2. VOLTAGE MONITOR (V) Pin and EXTERNAL CURRENT LIMIT (X) Pin Configuration Options.

Multi-Function Pin Table*

Figure Number 29 30 31 32 33 34 35 36 37 38 39 40

Three Terminal Operation

Line Undervoltage

Line Overvoltage

Line Feed-Forward (DC

Output Overvoltage Protection

Overload Power Limiting

External Current Limit

Remote ON/OFF

Device Reset

*This table is only a partial list of many MULTI-FUNCTIONAL Pin Configurations that are possible.

Table 3. MULTI-FUNCTION (M) Pin Configuration Options.

www.power.com

MAX

)

3

3 3 3 3

3 3 3 3

3 3 3

3 3

3

3 3 3 3

3 3 3

3

11

Rev. J 08/16

TOP252-262

M Pin

V Pin X Pin

Output

MOSFET

Switching

Current

Limit

Maximum

Duty Cycle

(Enabled)

(Disabled)

I

(Default)

LIMIT

DC

(78%)

MAX

I

REM(N)

I

UV

Disabled when supply
output goes out of
regulation

I

OV

I

OV(LS)

(Non-Latching) (Latching)

I

I

I

V

BG

Pin Voltage

-250 -200 -150 -100 -50 0 25 50 75 100 125 336

X and V Pins (Y, E, L and M Packages) and M Pin (P and G Packages) Current (µA)

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. For a detailed description of
each functional pin operation refer to the Functional Description section of the data sheet.

Figure 12. MULTI-FUNCTION (P and G package). VOLTAGE MONITOR and EXTERNAL CURRENT LIMIT (Y, E/L and M package) Pin Characteristics.

The circuit examples shown in Figures 41, 42 and 43 show a
simple method for implementing the primary sensed over­voltage protection.

The primary sensed OVP protection circuit shown in Figures 41,
42 and 43 is triggered by a significant rise in output voltage (and
therefore bias winding voltage). If the power supply is operating
under heavy load or low input line conditions when an open

During a fault condition resulting from loss of feedback, output
voltage will rapidly rise above the nominal voltage. The increase
in output voltage will also result in an increase in the voltage at
the output of the bias winding. A voltage at the output of the
bias winding that exceeds of the sum of the voltage rating of the
Zener diode connected from the bias winding output to the
V-pin (or M-pin) and V-pin (or M-pin) voltage, will cause a current
in excess of I

or IM to be injected into the V-pin

V

(or M-pin), which will trigger the OVP feature.

loop occurs, the output voltage may not rise significantly.
Under these conditions, a latching shutdown will not occur until
load or line conditions change. Nevertheless, the operation
provides the desired protection by preventing significant rise in
the output voltage when the line or load conditions do change.
Primary side OVP protection with the TOPSwitch-HX in a typical
application will prevent a nominal 12 V output from rising above
approximately 20 V under open loop conditions. If greater
accuracy is required, a secondary sensed OVP circuit is
recommended.

I

PI-4646-071708

12

Rev. J 08/16

www.power.com

TOP252-262

Line Feed-Forward with DC

Reduction

MAX

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. 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 DC

is also reduced from 78% (typical) at a voltage slightly

MAX

lower than the UV threshold to 36% (typical) at the OV threshold.
DC

of 36% at high line was chosen to ensure that the power

MAX

capability of the TOPSwitch-HX is not restricted by this feature
under normal operation. TOPSwitch-HX provides a better fit to the
ideal feed-forward by using two reduction slopes: -1% per mA for all
bus voltage less than 195 V (typical for 4 MW line impedance) and

-0.25% per mA for all bus voltage more than 195 V. This dual
slope line feed-forward improves the line ripple rejection
significantly compared with the TOPSwitch-GX.

Remote ON/OFF

TOPSwitch-HX can be turned on or off by controlling the
current into the VOLTAGE-MONITOR pin or out from the
EXTERNAL CURRENT LIMIT pin (Y, E/L and M packages) and
into or out from the MULTI-FUNCTION pin (P and G package,
see Figure 12). In addition, the VOLTAGE-MONITOR pin has a
1 V threshold comparator connected at its input. This voltage
threshold can also be used to perform remote ON/OFF control.

When a signal is received at the VOLTAGE-MONITOR pin or the
EXTERNAL CURRENT LIMIT pin (Y, E/L and M packages) or the
MULTI-FUNCTION pin (P and G package) to disable the output
through any of the pin functions such as OV, UV and remote
ON/OFF, TOPSwitch-HX always completes its current switching
cycle before the output is forced off.

As seen above, the remote ON/OFF feature can also be used as
a standby or power switch to turn off the TOPSwitch-HX and
keep it in a very low power consumption state for indefinitely
long periods. If the TOPSwitch-HX is held in remote off state for
long enough time to allow the CONTROL pin to discharge to the
internal supply undervoltage threshold of 4.8 V (approximately
32 ms for a 47

mF 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-HX 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/charge
cycle time of the CONTROL pin, which is approximately 125 ms
for a 47

mF 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

The 17 ms soft-start sweeps the peak drain current and
switching frequency linearly from minimum to maximum value
by operating through the low frequency PWM mode and the
variable frequency mode before entering the full frequency
mode. 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 (V

), due

C

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-HX 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 2% if
an out of regulation condition persists. Loss of regulation
interrupts the external current into the CONTROL pin. V

C

regulation changes from shunt mode to the hysteretic auto­restart mode as described in CONTROL pin operation section.
When the fault condition is removed, the power supply output
becomes regulated, V

regulation returns to shunt mode, and

C

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 (142 °C typical).
When the junction temperature cools to below the lower
hysteretic temperature point, normal operation resumes, thus
providing automatic recovery. A large hysteresis of 75 °C
(typical) is provided to prevent overheating of the PC board due
to a continuous fault condition. V

is regulated in hysteretic

C

mode, and a 4.8 V to 5.8 V (typical) triangular waveform is
present on the CONTROL pin while in thermal shutdown.

Bandgap Reference

All critical TOPSwitch-HX internal voltages are derived from a
temperature-compensated bandgap reference. This voltage
reference is used to generate all other internal current
references, which are trimmed to accurately set the switching
frequency, MOSFET gate drive current, current limit, and the line
OV/UV/OVP thresholds. TOPSwitch-HX has improved circuitry
to maintain all of the above critical parameters within very tight
absolute and temperature tolerances.

High-Voltage Bias Current Source

This high-voltage current source biases TOPSwitch-HX 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 approxi­mately 35%. This duty cycle is determined by the ratio of
CONTROL pin charge (I

) and discharge currents (I

C

CD1

and I

CD2

).
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.

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13

Rev. J 08/16

TOP252-262

CONTROL (C)

EXTERNAL CURRENT LIMIT (X)

Y, E/L and M Package

200 µA

VBG + V

TOPSwitch-HX

(Negative Current Sense - ON/OFF,

Current Limit Adjustment)

T

VOLTAGE MONITOR (V)

V

REF

400 µA

Figure 13a. VOLTAGE MONITOR (V) and EXTERNAL CURRENT LIMIT (X) Pin Input Simplified Schematic.

P and G Package

CONTROL (C)

MULTI-FUNCTION (M)

200 µA

VBG + V

(Negative Current Sense - ON/OFF,

T

V

REF

TOPSwitch-HX

Current Limit Adjustment)

(Positive Current Sense - Undervoltage,

Overvoltage, Maximum Duty Cycle Reduction,

Output Overvoltage Protection)

(Voltage Sense)

1 V

(Positive Current Sense - Undervoltage,

Overvoltage, ON/OFF, Maximum Duty

Cycle Reduction, Output Over-

voltage Protection)

PI-4714-071408

Figure 13b. MULTI-FUNCTION (M) Pin Input Simplified Schematic.

14

Rev. J 08/16

400 µA

PI-4715-071408

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Typical Uses of FREQUENCY (F) Pin

TOP252-262

+

DC

Input

Voltage

D

S

CONTROL

C

F

-

PI-2654-071700

Figure 14. Full Frequency Operation (132 kHz). Figure 15. Half Frequency Operation (66 kHz).

+

DC

Input

Voltage

-

D

CONTROL

S

C

F

PI-2655-071700

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15

Rev. J 08/16