Datasheet TNY255P, TNY255G, TNY254P, TNY254G, TNY253G Datasheet (Power Integrations)

®

TNY253/254/255

®

TinySwitch

Energy Efficient, Low Power Off-line Switchers

Product Highlights

Family

Lowest Cost, Low Power Switcher Solution

• Lower cost than RCC, discrete PWM and other
integrated/hybrid solutions

• Cost effective replacement for bulky linear adapters

• Lowest component count

• Simple ON/OFF control – no loop compensation devices

• No bias winding – simpler, lower cost transformer

• Allows simple RC type EMI filter for up to 2 W from

universal input or 4 W from 115 VAC input

Extremely Energy Efficient

• Consumes only 30/60 mW at 115/230 VAC with no load

• Meets Blue Angel, Energy Star, Energy 2000 and

200mW European cell phone requirements for standby

• Saves $1 to $4 per year in energy costs (at $0.12/kWHr)
compared to bulky linear adapters

• Ideal for cellular phone chargers, standby power supplies
for PC, TV and VCR, utility meters, and cordless phones.

High Performance at Low Cost

• High voltage powered – ideal for charger applications

• Very high loop bandwidth provides excellent transient

response and fast turn on with practically no overshoot

• Current limit operation rejects line frequency ripple

• Glitch free output when input is removed

• Built-in current limit and thermal protection

• 44 kHz operation (TNY253/4) with snubber clamp

reduces EMI and video noise in TVs & VCRs

• Operates with optocoupler or bias winding feedback

+

Wide-Range
HV DC Input

–

Figure 1. Typical Standby Application.

TinySwitch

ORDER

PART

NUMBER

TNY253P
TNY253G
TNY254P

TNY254G
TNY255P
TNY255G

PACKAGE

DIP-8

SMD-8

DIP-8

SMD-8

DIP-8

SMD-8

TinySwitch

D

EN
BP

S

SELECTION GUIDE

Recommended Range

for Lowest System Cost*

230 VAC or

115 VAC

w/Doubler

0-4 W

2-5 W

+

DC Output

–

PI-2178-022699

85-265

VAC

0-2 W

1-4 W

3.5-6.5 W4-10 W

Description

The TinySwitch family uses a breakthrough design to provide
the lowest cost, high efficiency, off-line switcher solution in the
0 to 10 W range. These devices integrate a 700 V power
MOSFET, oscillator, high voltage switched current source,
current limit and thermal shutdown circuitry. They start-up and
run on power derived from the DRAIN voltage, eliminating the
need for a transformer bias winding and the associated circuitry.
And yet, they consume only about 80 mW at no load, from
265VAC input. A simple ON/OFF control scheme also
eliminates the need for loop compensation.

The TNY253 and TNY254 switch at 44 kHz to minimize EMI
and to allow a simple snubber clamp to limit DRAIN spike

Table 1. *Please refer to the Key Application Considerations section
for details.

voltage. At the same time, they allow use of low cost EE16 core
transformers to deliver up to 5 W. The TNY253 is identical to
TNY254 except for its lower current limit, which reduces
output short circuit current for applications under 2.5W.
TNY255 uses higher switching rate of 130kHz to deliver up to
10 W from the same low cost EE16 core for applications such
as PC standby supply. An EE13 or EF13 core with safety
spaced bobbin can be used for applications under 2.5W.
Absence of a bias winding eliminates the need for taping/
margins in most applications, when triple insulated wire is used
for the secondary. This simplifies the transformer construction
and reduces cost.

July 2001

TNY253/254/255

S

Q

Q

BYPASS

ENABLE

50 µA

OSCILLATOR

1.5 V + V
TH

CLOCK

DC

MAX

5.8 V

5.1 V

Figure 2. Functional Block Diagram.

Pin Functional Description

DRAIN (D) Pin:

Power MOSFET drain connection. Provides internal operating
current for both start-up and steady-state operation.

BYPASS (BP) Pin:

Connection point for an external bypass capacitor for the
internally generated 5.8V supply. Bypass pin is not intended
for sourcing supply current to external circuitry.

UNDER-VOLTAGE

+

-

THERMAL

SHUTDOWN

REGULATOR

5.8 V

BYPASS

SOURCE

SOURCE

ENABLE

1

2

3

4

P Package (DIP-8)

G Package (SMD-8)

Figure 3. Pin Configuration.

LEADING

EDGE

BLANKING

+

-

8

7

6

5

V

I

LIMIT

SOURCE

SOURCE

SOURCE

DRAIN

DRAIN

SOURCE

PI-2197-061898

PI-2199-031501

ENABLE (EN) Pin:

The power MOSFET switching can be terminated by pulling
this pin low. The I-V characteristic of this pin is equivalent to
a voltage source of approximately 1.5V with a source current
clamp of 50 µA.

SOURCE (S) Pin:

Power MOSFET source connection. Primary return.

TinySwitch

Functional Description

circuit, Hysteretic Over Temperature Protection, Current Limit
circuit, Leading Edge Blanking, and a 700V power MOSFET.
Figure 2 shows a functional block diagram with the most
important features.

Oscillator

The oscillator frequency is internally set at 44 kHz (130 kHz for
the TNY255). The two signals of interest are the Maximum
Duty Cycle signal (D

) which runs at typically 67% duty

MAX

cycle and the Clock signal that indicates the beginning of each

cycle. When cycles are skipped (see below), the oscillator
TinySwitch is intended for low power off-line applications. It
combines a high voltage power MOSFET switch with a power
supply controller in one device. Unlike a conventional PWM

frequency doubles (except for TNY255 which remains at

130kHz). This increases the sampling rate at the ENABLE pin

for faster loop response.
(Pulse Width Modulator) controller, the TinySwitch uses a
simple ON/OFF control to regulate the output voltage.

Enable (Sense and Logic)

The ENABLE pin circuit has a source follower input stage set
The TinySwitch controller consists of an Oscillator, Enable
(Sense and Logic) circuit, 5.8V Regulator, Under-Voltage

C

2

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at 1.5V. The input current is clamped by a current source set

at 50 µA with 10 µA hysteresis. The output of the enable sense

TNY253/254/255

circuit is sampled at the rising edge of the oscillator Clock
signal (at the beginning of each cycle). If it is high, then the
power MOSFET is turned on (enabled) for that cycle, otherwise
the power MOSFET remains in the off state (cycle skipped).
Since the sampling is done only once at the beginning of each
cycle, any subsequent changes at the ENABLE pin during the
cycle are ignored.

5.8 V Regulator

The 5.8 V regulator charges the bypass capacitor connected to
the BYPASS pin to 5.8V by drawing a current from the voltage
on the DRAIN, whenever the MOSFET is off. The BYPASS
pin is the internal supply voltage node for the TinySwitch.
When the MOSFET is on, the TinySwitch runs off of the energy
stored in the bypass capacitor. Extremely low power
consumption of the internal circuitry allows the TinySwitch to
operate continuously from the current drawn from the DRAIN
pin. A bypass capacitor value of 0.1 µF is sufficient for both
high frequency de-coupling and energy storage.

Under Voltage

The under-voltage circuitry disables the power MOSFET when
the BYPASS pin voltage drops below 5.1V. Once the BYPASS
pin voltage drops below 5.1 V, it has to rise back to 5.8V to
enable (turn-on) the power MOSFET.

Hysteretic Over Temperature Protection

The thermal shutdown circuitry senses the die junction
temperature. The threshold is set at 135 °C with 70 °C hysteresis.
When the junction temperature rises above this threshold
(135 °C) the power MOSFET is disabled and remains disabled
until the die junction temperature falls by 70 °C, at which point
it is re-enabled.

Current Limit

The current limit circuit senses the current in the power
MOSFET. When this current exceeds the internal threshold
(I

), the power MOSFET is turned off for the remainder of

LIMIT

that cycle.

device are constant, the power delivered is proportional to the
primary inductance of the transformer and is relatively
independent of the input voltage. Therefore, the design of the
power supply involves calculating the primary inductance of
the transformer for the maximum power required. As long as
the TinySwitch device chosen is rated for the power level at the
lowest input voltage, the calculated inductance will ramp up the
current to the current limit before the DC

limit is reached.

MAX

Enable Function

The TinySwitch senses the ENABLE pin to determine whether
or not to proceed with the next switch cycle as described earlier.
Once a cycle is started TinySwitch always completes the cycle
(even when the ENABLE pin changes state half way through
the cycle). This operation results in a power supply whose
output voltage ripple is determined by the output capacitor,
amount of energy per switch cycle and the delay of the ENABLE
feedback.

The ENABLE signal is generated on the secondary by comparing
the power supply output voltage with a reference voltage. The
ENABLE signal is high when the power supply output voltage
is less than the reference voltage.

In a typical implementation, the ENABLE pin is driven by an
optocoupler. The collector of the optocoupler transistor is
connected to the ENABLE pin and the emitter is connected to
the SOURCE pin. The optocoupler LED is connected in series
with a Zener across the DC output voltage to be regulated.
When the output voltage exceeds the target regulation voltage
level (optocoupler diode voltage drop plus Zener voltage), the
optocoupler diode will start to conduct, pulling the ENABLE
pin low. The Zener could be replaced by a TL431 device for
improved accuracy.

The ENABLE pin pull-down current threshold is nominally
50 µA, but is set to 40 µA the instant the threshold is exceeded.
This is reset to 50 µA when the ENABLE pull-down current
drops below the current threshold of 40 µA.

The leading edge blanking circuit inhibits the current limit
comparator for a short time (t

) after the power MOSFET is

LEB

turned on. This leading edge blanking time has been set so that
current spikes caused by primary-side capacitance and
secondary-side rectifier reverse recovery time will not cause
premature termination of the switching pulse.

TinySwitch

Operation

TinySwitch is intended to operate in the current limit mode.
When enabled, the oscillator turns the power MOSFET on at
the beginning of each cycle. The MOSFET is turned off when
the current ramps up to the current limit. The maximum on­time of the MOSFET is limited to DC

by the oscillator.

MAX

Since the current limit and frequency of a given TinySwitch

ON/OFF Control

The internal clock of the TinySwitch runs all the time. At the
beginning of each clock cycle the TinySwitch samples the
ENABLE pin to decide whether or not to implement a switch
cycle. If the ENABLE pin is high (< 40 µA), then a switching
cycle takes place. If the ENABLE pin is low (greater than
50 µA) then no switching cycle occurs, and the ENABLE pin
status is sampled again at the start of the subsequent clock cycle.

At full load TinySwitch will conduct during the majority of its
clock cycles (Figure 4). At loads less than full load, the
TinySwitch will “skip” more cycles in order to maintain voltage
regulation at the secondary output (Figure 5). At light load or
no load, almost all cycles will be skipped (Figure 6). A small

C

3

7/01

TNY253/254/255

V

EN

CLOCK

DC

MAX

I

DRAIN

V

DRAIN

PI-2255-061298

Figure 4. TinySwitch Operation at Heavy Load. Figure 5. TinySwitch Operation at Medium Load.

percentage of cycles will conduct to support the power
consumption of the power supply.

V

EN

CLOCK

DC

MAX

I

DRAIN

V

DRAIN

inductance and input voltage, the duty cycle is constant.
However, duty cycle does change inversely with the input

voltage providing “voltage feed-forward” advantages: good
The response time of TinySwitch ON/OFF control scheme is
very fast compared to normal PWM control. This provides high

line ripple rejection and relatively constant power delivery

independent of the input voltage.
line ripple rejection and excellent transient response.

44 kHz Switching Frequency (TNY253/254)
Power Up/Down

TinySwitch requires only a 0.1 µF capacitor on the BYPASS
pin. Because of the small size of this capacitor, the power-up
delay is kept to an absolute minimum, typically 0.3 ms (Figure7).
Due to the fast nature of the ON/OFF feedback, there is no
overshoot at the power supply output. During power-down, the
power MOSFET will switch until the rectified line voltage
drops to approximately 12 V. The power MOSFET will then
remain off without any glitches (Figure 8).

Switching frequency (with no cycle skipping) is set at 44kHz.

This provides several advantages. At higher switching

frequencies, the capacitive switching losses are a significant

proportion of the power losses in a power supply. At higher

frequencies, the preferred snubbing schemes are RCD or diode-

Zener clamps. However, due to the lower switching frequency

of TinySwitch , it is possible to use a simple RC snubber (and

even just a capacitor alone in 115VAC applications at powers

levels below 4W).

PI-2259-061298

Bias Winding Eliminated

TinySwitch does not require a bias winding to provide power to
the chip. Instead it draws the power directly from the DRAIN
pin (see Functional Description above). This has two main
benefits. First for a nominal application, this eliminates the cost
of an extra bias winding and associated components. Secondly,
for charger applications, the current-voltage characteristic often
allows the output voltage to fall to low values while still
delivering power. This type of application normally requires a
forward-bias winding which has many more associated
components, none of which are necessary with TinySwitch.

Current Limit Operation

Each switching cycle is terminated when the DRAIN current
reaches the current limit of the TinySwitch. For a given primary

C

4

7/01

Secondly, a low switching frequency also reduces EMI filtering

requirements. At 44kHz, the first, second and third harmonics

are all below 150kHz where the EMI limits are not very

restrictive. For power levels below 4W it is possible to meet

worldwide EMI requirements with only resistive and capacitive

filter elements (no inductors or chokes). This significantly

reduces EMI filter costs.

Finally, if the application requires stringent noise emissions

(such as video applications), then the TNY253/254 will allow

more effective use of diode snubbing (and other secondary

snubbing techniques). The lower switching frequency allows

RC snubbers to be used to reduce noise, without significantly

impacting the efficiency of the supply.

TNY253/254/255

V

EN

CLOCK

DC

MAX

I

DRAIN

V

DRAIN

PI-2261-061198

Figure 6. TinySwitch Operation at Light Load.

130 kHz Switching Frequency (TNY255)

The switching frequency (with no cycle skipping) is set at
130kHz. This allows the TNY255 to deliver 10W while still
using the same size, low cost transformer (EE16) as used by the
TNY253/254 for lower power applications.

BYPASS Pin Capacitor

The BYPASS pin uses a small 0.1 µF ceramic capacitor for
decoupling the internal power supply of the TinySwitch.

V

IN

V

DRAIN

0.2

Figure 7. TinySwitch Power-Up Timing Diagram.

V

IN

V

DRAIN

.4

Time (ms)

.6 .8

12 V

12 V

PI—2253-062398

0 V

0 V

1

PI—2251-062398

0 V

0 V

Application Examples

Television Standby

TinySwitch is an ideal solution for low cost, high efficiency
standby power supplies used in consumer electronic products
such as TVs. Figure9 shows a 7.5 V, 1.3 W flyback circuit that
uses TNY253 for implementing a TV standby supply. The
circuit operates from the DC high voltage already available
from the main power supply. This input voltage can range from
120 to 375VDC depending on the input AC voltage range that
the TV is rated for. Capacitor C1 filters the high voltage DC
supply, and is necessary only if there is a long trace length from
the source of the DC supply to the inputs of the TV standby
circuit. The high voltage DC bus is applied to the series
combination of the primary winding of T1 and the integrated
high voltage MOSFET inside the TNY253. The low operating
frequency of the TNY253 (44kHz), allows a low cost snubber
circuit C2 and R1 to be used in place of a primary clamp circuit.
In addition to limiting the DRAIN turn off voltage spike to a
safe value, the RC snubber also reduces radiated video noise by

0 100

Figure 8. TinySwitch Power Down Timing Diagram.

200

Time (ms)

300 400

500

lowering the dv/dt of the DRAIN waveform, which is critical for

video applications such as TV and VCR. On fixed frequency

PWM and RCC circuits, use of a snubber will result in an

undesirable fixed AC switching loss that is independent of load.

The ON/OFF control on the TinySwitch eliminates this problem

by scaling the effective switching frequency and therefore,

switching loss linearly with load. Thus the efficiency of the

supply stays relatively constant down to a fraction of a watt of

output loading.

The secondary winding is rectified and filtered by D1 and C4 to

create the 7.5V output. L1 and C5 provide additional filtering.

The output voltage is determined by the sum of the optocoupler

U2 LED forward drop (~ 1 V) and Zener diode VR1 voltage.

The resistor R2, maintains a bias current through the Zener to

improve its voltage tolerance.

C

5

7/01

TNY253/254/255

+

DC IN

120-375 VDC

Optional

C1

0.01 µF
1 kV

R1

100 Ω

1/2 W

C2

56 pF

1 kV

–

Figure 9. 1.3 W TV Stand-by Circuit using TNY253.

R1

150 kΩ

1 W

Optional

240-375

VDC

C1

0.01 µF
1 kV

TNY253P

C2

4700 pF

1 kV

1N4937

TNY255P

D1

U1

U1

T1

1

4

TinySwitch

D

EN
BP

S

0.1 µF

T1

1

4

TinySwitch

D

EN

BP

S

1N4934

10

8

C3

10

8

D1

C6

680 pF

Y1 Safety

D2

SB540

U2

LTV817

15 µH

330 µF

10 V

U2

SFH615-2

R2

1 kΩ

VR1

1N5235B

C4

2700 µF

6.3 V

C4

L1

L1

10 µH

R2

68 Ω

C5

47 µF

10 V

C5

220 µF

10 V

+ 7.5 V

RTN

PI-2246-082898

+ 5 V

RTN

Figure 10. 10 W PC Stand-by Supply Circuit.

PC Standby

The TNY255 was designed specifically for applications such as
PC standby, which require up to 10W of power from 230VAC
or 100/115VAC with doubler circuit. The TNY255 operates at
130kHz as opposed to 44kHz for TNY253/254. The higher
frequency operation allows the use of a low cost EE16 core
transformer up to the 10W level. Figure10 shows a 5V, 10W
circuit for such an application. The circuit operates from the
high voltage DC supply already available from the main power
supply. Capacitor C1 filters the high voltage DC supply, and is
necessary only if there is a long trace length from the source of
the DC supply to the inputs of the PC standby circuit. The high
voltage DC bus is applied to the primary winding of T1 in series

C

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7/01

C3

0.1 µF
VR1

1N5229B

PI-2242-082898

with the integrated high voltage MOSFET inside the TNY255.
The diode D1, capacitor C2 and resistor R1 comprise the clamp
circuit that limits the turn-off voltage spike on the TinySwitch
DRAIN pin to a safe value. The secondary winding is rectified
and filtered by D2 and C4 to provide the 5V ouput. Additional
filtering is provided by L1 and C5. The output voltage is
determined by the sum of the optocoupler U2 LED forward
drop (~ 1V) and Zener diode VR1 voltage. The resistor R2,
maintains a bias current through the Zener to improve its
voltage tolerance.

Cellular Phone Charger

The TinySwitch is well suited for applications that require a

TNY253/254/255

FR201

T1

10

1

C4

2200 pF

D6

1N4937

U1

TNY254P

2

TinySwitch

D

EN

BP

S

LTV817

5

U2

C3

0.1 µF

Y1 Safety

85-265

VAC

D1

1N4005

RF1

10 Ω

Fusible

D3

1N4005

D2

1N4005

D4

1N4005

C1

6.8 µF
400 V

R2

100 kΩ

1 W

C2

4.7 µF
400 V

R1

1.2 kΩ

L1

560 µH

Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger Circuit.

D5

Q1

2N3904

C8

2.2 nF

R9

47 Ω

C5

220 µF

25 V

R3

22 Ω

R5

18 Ω

1/8 W

R4

1 Ω

1 W

R7

100 Ω

0.82 Ω

R6

1/2 W

L2

3.3 µH

C6

220 µF

16 V

R8

820 Ω

VR1

1N5230B

4.7 V

+ 5.2 V

RTN

PI-2244-082898

D1

1N4004

115 VAC

± 15%

RF1

1.8 Ω

Fusible

C1

2.2 µF
200 V

D2

1N4004

C2

2.2 µF
200 V

R2

100 Ω

C4

68 pF

1 KV

Figure 12. 0.5 W Open Loop AC Adapter Circuit.

constant voltage and constant current output. TinySwitch is
always powered from the input high voltage, therefore it does
not require bias winding for power. Consequently, its operation
is not dependent on the level of the output voltage. This allows
for constant current charger designs that work down to zero
volts on the output.

Figure11 shows a 5.2V, 3.6W cellular phone charger circuit
that uses the TNY254 and provides constant voltage and constant
current output over an universal input (85 to 265VAC) range.
The AC input is rectified and filtered by D1 - D4, C1 and C2 to

D3

1N3934

T1

10

U1

TNY253P

1

5

TinySwitch

D

EN

BP

S

C3

0.1 µF

6

C6

100 µF

16V

C5

2.2 nF

Y1 Safety

VR1

1N5239B

+ 9 V

RTN

create a high voltage DC bus connected to T1 in series with the
high voltage MOSFET inside the TNY254. The inductor L1
forms a π-filter in conjunction with C1 and C2. The resistor R1
damps resonances in the inductor L1. The low frequency of
operation of TNY254 (44kHz) allows use of the simple π-filter
described above in combination with a single Y1-capacitor C8
to meet worldwide conducted EMI standards. The diode D6,
capacitor C4 and resistor R2 comprise the clamp circuit that
limits the turn-off voltage spike on the TinySwitch DRAIN pin
to a safe value. The secondary winding is rectified and filtered
by D5 and C5 to provide the 5.2V output. Additional filtering

PI-2190-031501

7/01

C

7

TNY253/254/255

is provided by L2 and C6. The output voltage is determined by
the sum of the optocoupler U2 LED forward drop (~ 1V) and
Zener diode VR1 voltage. The resistor R8, maintains a bias
current through the Zener to improve its voltage tolerance.

A simple constant current circuit is implemented using the V
of transistor Q1 to sense the voltage across the current sense
resistor R4, which can be made up of one or more resistors to
achieve the appropriate value. R3 is a base current limiting
resistor. When the drop across R4 exceeds the VBE of transistor
Q1, it turns on and takes over the control of the loop by driving
the optocoupler LED. R6 drops an additional voltage to keep the
control loop in operation down to zero volts on the output. With
the output shorted, the drop across R4 and R6 (~ 1.5V) is
sufficient to keep the Q1 and LED circuit active. Resistors R7
and R9 limit the forward current that could be drawn through
VR1 by Q1 under output short circuit conditions, due to the
voltage drop across R6 and R4.

AC Adapter

Many consumer electronic products utilize low power 50/60Hz
transformer based AC adapters. The TinySwitch can cost
effectively replace these linear adapters with a solution that is
lighter, smaller and more energy efficient . Figure12 shows a
9V, 0.5W AC adapter circuit using the TNY253. This circuit
operates from a 115VAC input. To save cost, this circuit runs
without any feedback, in discontinuous conduction mode to
deliver constant power output relatively independent of input
voltage. The output voltage is determined by the voltage drop
across Zener diode VR1. The primary inductance of the
transformer is chosen to deliver a power that is in excess of the
required output power by at least 50% to allow for component
tolerances and to maintain some current through the Zener VR1
at full load. At no load, all of the power is delivered to the Zener
which should be rated and heat sinked accordingly. In spite of
a constant power consumption from the mains input, this solution
is still significantly more efficient than linear adapters up to
output power levels of approximately 1W.

Key Application Considerations

For the most up to date information visit our Web site
at: www.powerint.com

BE

Design

Output Power Range

The power levels shown in the TinySwitch Selection Guide
(Table 1) are approximate, recommended output power ranges
that will provide a cost optimum design and are based on
following assumptions:

1. The minimum DC input voltage is 90 V or higher for
85VAC input or 240V or higher for 230 VAC input or
115VAC input with a voltage doubler.

2. The TinySwitch is not thermally limited-the source pins are

soldered to sufficient copper area to keep the die temperature
at or below 100 °C. This limitation does not usually apply
to TNY253 and TNY254.

The maximum power capability of a TinySwitch depends on the
thermal environment, transformer core size and design
(continuous or discontinuous), efficiency required, minimum
specified input voltage, input storage capacitance, output
voltage, output diode forward drop, etc., and can be different
from the values shown in the selection guide.

Audible Noise

At loads other than maximum load, the cycle skipping mode
operation used in TinySwitch can generate audio frequency
components in the transformer. This can cause the transformer
to produce audio noise. Transformer audible noise can be
reduced by utilizing appropriate transformer construction
techniques and decreasing the peak flux density. For more
information on audio suppression techniques, please check
the Application Notes section on our Web site at
www.powerint.com.

The AC input is rectified by diodes D1 and D2. D2 is used to
reduce conducted EMI by only allowing noise onto the neutral
line during diode conduction. The rectified AC is then filtered
by capacitors C1 and C2 to generate a high voltage DC bus,
which is applied to the series combination of the primary
winding of T1 and the high voltage MOSFET inside the TNY253.
The resistor R2 along with capacitors C1 and C2 form a π-filter
which is sufficient for meeting EMI conducted emissions at
these power levels. C5 is a Y-capacitor which is used to reduce
common mode EMI. Due to the 700V rating of the TinySwitch
MOSFET, a simple capacitive snubber (C4) is adequate to limit
the leakage inductance spike in 115VAC applications, at low
power levels. The secondary winding is rectified and filtered by
D3 and C6.

C

8

7/01

Ceramic capacitors that use dielectrics such as Z5U, when used
in clamp and snubber circuits, can also generate audio noise due
to electrostriction and piezo-electric effects. If this is the case,
replacing them with a capacitor having a different type of
dielectric is the simplest solution. Polyester film capacitor is a
good alternative.

Short Circuit Current

The TinySwitch does not have an auto-restart feature. As a
result, TinySwitch will continue to deliver power to the load
during output short circuit conditions. In the worst case, peak
short circuit current is equal to the primary current limit (I

LIMIT

multiplied by the turns ratio of the transformer (Np/Ns). In a
typical design the average current is 25 to 50% lower than this
peak value. At the power levels of TinySwitch this is easily

)

+

HV

–

TOP VIEW

Input Filter Capacitor

S

TinySwitch

C

BP

Safety Spacing

Transformer

PRI

D

Y1-

Capacitor

Opto-

coupler

SEC

Output Filter Capacitor

DC

+–

Out

TNY253/254/255

Maximize hatched copper
areas ( ) for optimum
heat sinking

BP

Figure 13. Recommended PC Layout for the TinySwitch.

S

EN

accommodated by rating the output diode to handle the short
circuit current. The short circuit current can be minimized by
choosing the smallest (lowest current limit) TinySwitch for the
required power.

Layout

Single Point Grounding

Use a single point ground connection at the SOURCE pin for the
BYPASS pin capacitor and the Input Filter Capacitor (see
Figure 13).

Primary Loop Area

The area of the primary loop that connects the input filter
capacitor, transformer primary and TinySwitch together, should
be kept as small as possible.

Primary Clamp Circuit

A clamp or snubber circuit is used to minimize peak voltage and
ringing on the DRAIN pin at turn-off. This can be achieved by
using an RC snubber for less than 3 W or an RCD clamp as
shown in Figure 13 for higher power. A Zener and diode clamp
across the primary or a single 550V Zener clamp from DRAIN
to SOURCE can also be used. In all cases care should be taken
to minimize the circuit path from the snubber/clamp components
to the transformer and TinySwitch.

Thermal Considerations

Copper underneath the TinySwitch acts not only as a single point
ground, but also as a heatsink. The hatched area shown in
Figure13 should be maximized for good heat-sinking of
TinySwitch and output diode.

PI-2176-071398

Y-Capacitor

The placement of the Y-capacitor should be directly from the
primary single point ground to the common/return terminal on
the secondary side. Such placement will maximize the EMI
benefit of the Y-capacitor.

Optocoupler

It is important to maintain the minimum circuit path from the
optocoupler transistor to the TinySwitch ENABLE and SOURCE
pins to minimize noise coupling.

Output Diode

For best performance, the area of the loop connecting the
secondary winding, the Output Diode and the Output Filter
Capacitor, should be minimized. See Figure13 for optimized
layout. In addition, sufficient copper area should be provided
at the anode and cathode terminals of the diode to adequately
heatsink the diode under output short circuit conditions.

Input and Output Filter Capacitors

There are constrictions in the traces connected to the input and
output filter capacitors. These constrictions are present for two
reasons. The first is to force all the high frequency currents to
flow through the capacitor (if the trace were wide then it could
flow around the capacitor). Secondly, the constrictions minimize
the heat transferred from the TinySwitch to the input filter
capacitor and from the secondary diode to the output filter
capacitor. The common/return (the negative output terminal in
Figure13) terminal of the output filter capacitor should be
connected with a short, low resistance path to the secondary
winding. In addition, the common/return output connection
should be taken directly from the secondary winding pin and
not from the Y-capacitor connection point.

7/01

C

9

TNY253/254/255

ABSOLUTE MAXIMUM RATINGS

DRAIN Voltage ....................................... - 0.3 V to 700 V

Peak DRAIN Current (TNY253/4) ........................400 mA

Peak DRAIN Current (TNY255) ...........................530 mA

ENABLE Voltage ........................................ - 0.3 V to 9 V

ENABLE Current...................................................100 mA

BYPASS Voltage.......................................... -0.3 V to 9 V

1. All voltages referenced to SOURCE, TA = 25 °C.

2. Normally limited by internal circuitry.

3. 1/16" from case for 5 seconds.

Conditions

Parameter

Symbol

SOURCE = 0 V; TJ = -40 to 125 °C

See Figure 14

(Unless Otherwise Specified)

CONTROL FUNCTIONS

Output
Frequency

Maximum
Duty Cycle

ENABLE Pin Turnoff
Threshold Current

f

DC

OSC

I

DIS

S1 Open

MAX

TJ = 25 °C

T

= -40 °C to 125 °C

J

T

(1)

Storage Temperature ..................................... -65 to 150 °C

Operating Junction Temperature
Lead Temperature

(3)

................................................ 260 °C

Thermal Impedance (θJA) ................ 45 °C/W

(2)

................-40 to 150 °C

(4)

, 35 °C/W

Thermal Impedance (θJC) ..................................... 11 °C/W

4. Soldered to 0.36 sq. inch (232 mm2), 2 oz. (610 gm/m2) copper clad.

5. Soldered to 1 sq. inch (645 mm2), 2 oz. (610 gm/m2) copper clad.

Min Typ Max

= 125 °C

J

TNY253
TNY254

TNY255

TNY253
TNY254

TNY255

40 44 48

115 140

130
66 68 71
64 69

67

-68 -50 -30

-68

-52

-45

(5)

Units

kHz

%

µA

ENABLE Pin
Hysteresis Current

ENABLE Pin
Voltage

ENABLE Short­Circuit Current

DRAIN
Supply Current

BYPASS Pin
Charge Current

BYPASS Pin
Voltage

BYPASS
Hysteresis

I

V

I

I

I

V

V

HYS

EN

ENSC

I

S1

I

S2

CH1

CH2

BP

BPH

See Note A

IEN = -25 µA

VEN = 0 V, T

VEN = 0 V, T

V

= -40 °C to 125 °C

J

= 125 °C

J

= 0 V

EN

(MOSFET Not Switching)
See Note B

ENABLE Open

(MOSFET Switching)

See Note B, C

VBP = 0 V, TJ = 25 °C

See Note D, E

VBP = 4 V, TJ = 25 °C

See Note D, E

See Note D

TNY253
TNY254

TNY255
TNY253

TNY254
TNY255

TNY253
TNY254

TNY255
TNY253

TNY254
TNY255

-15 -10 -5

1.10 1.45 1.80

-58 -42 -25

-58

-45 -38
160 200
170 215
140 180

215

-5.0

-6.0

-4.0 -1.0

-4.8

5.6 6.1

0.60 0.85

-3.5

-4.5

-2.5

-3.3

5.8

0.72

265

-2.0

-3.0

-1.8

µA

V

µA

µA

µA

mA

mA

V

V

10

C
7/01

Conditions

Parameter Symbol SOURCE = 0 V; T

See Figure 14

(Unless Otherwise Specified)

CIRCUIT PROTECTION

= -40 to 125 °C

J

Min

TNY253/254/255

Typ Max

Units

Current Limit

Initial Current
Limit

Leading Edge
Blanking Time

Current Limit
Delay

Thermal Shutdown
Temperature

Thermal Shutdown
Hysteresis

OUTPUT

ON-State
Resistance

OFF-State
Leakage

Breakdown
Voltage

Note F

R

BV

I

LIMIT

I

INIT

t

LEB

t

ILD

DS(ON)

I

DSS

DSS

di/dt = 12.5 mA/µs

TJ = 25 °C

di/dt = 25 mA/µs

TJ = 25 °C

di/dt = 80 mA/µs

TJ = 25 °C

See Figure 17

TJ = 25 °C

TJ = 25 °C

See Note G

TNY253/TNY254

ID = 25 mA

TNY255

ID = 33 mA

VBP = 6.2 V, V

V

= 560 V, TJ = 125 °C

DS

VBP = 6.2 V, V

I

= 100 µA, TJ = 25 °C

DS

TJ = 25 °C

EN

EN

TNY253

TNY254

TNY255

TNY253
TNY254

TNY255
TNY253
TNY254
TNY255

T

= 25 °C

J

TJ = 100 °C

T

= 25 °C

J

TJ = 100 °C

= 0 V,

= 0 V,

135 150 165

230 255 280

255 280 310

0.65 x

I

LIMIT(MIN)

170 240
170 215

200 250
100 150

125 135 145

70

31 36
50 60

23 27
37 45

700

50

mA

mA

ns

ns

°C

°C

Ω

µA

V

Rise Time

Fall Time

t

R

50

ns

Measured with Figure 10

Schematic.

t

F

50

7/01

ns

C

11

TNY253/254/255

Parameter Symbol SOURCE = 0 V; T

(Unless Otherwise Specified)

OUTPUT (cont.)

Conditions

= -40 to 125 °C

See Figure 14

J

Min

Typ

Max

Units

DRAIN Supply

50

V

Voltage
Output Enable

Delay
Output Disable

Setup Time

t

t

DST

EN

See Figure 16

NOTES:

A. For a threshold with a negative value, negative hysteresis is a decrease in magnitude of the corresponding threshold.
B. Total current consumption is the sum of IS1 and I

and the sum of IS2 and I

when ENABLE pin is open (MOSFET switching).

DSS

when ENABLE pin is shorted to ground (MOSFET not switching)

DSS

C. Since the output MOSFET is switching, it is difficult to isolate the switching current from the supply current at the

DRAIN. An alternative is to measure the BYPASS pin current at 6.2 V.
D. Bypass pin is not intended for sourcing supply current to external circuitry.
E. See typical performance characteristics section for BYPASS pin start-up charging waveform.
F. For current limit at other di/dt values, refer to current limit vs. di/dt curve under typical performance

characteristics.

TNY253
TNY254

TNY255

0.5

14
10

µs

µs

G. This parameter is derived from the change in current limit measured at 5X and 10X of the di/dt shown in the I

specification.

DEN

S

S

S

S

BPS

470 Ω

5 W

S1

10 V

0.1 µF

S2

470 Ω

50 V

NOTE: This test circuit is not applicable for current limit or output characteristic measurements.

PI-2211-061898

Figure 14. TinySwitch General Test Circuit.

C

12

7/01

LIMIT

1.2

1.0

0.8

0.6

0.4

0.2

0

-50 -25 0 25 50 75 100 125

Junction Temperature (°C)

FREQUENCY vs. TEMPERATURE

PI-2238-033001

Output Frequency

(Normalized to 25 °C)

HV

90%

TNY253/254/255

DC

t

2

t

1

90%

MAX

ENABLE

t

P

DRAIN

VOLTAGE

10%

0 V

Figure 15. TinySwitch Duty Cycle Measurement.

t

1

D =

t

2

PI-2048-033001

Figure 16. TinySwitch Output Enable Timing.

t

(Blanking Time)

1.3

1.2

1.1

1.0

0.9

0.8

0.8

0.7

0.6

0.5

0.4

0.3

0.2

DRAIN Current (normalized)

0.1
0

LEB

I

INIT(MIN)

I

LIMIT(MAX)

I

LIMIT(MIN)

012 6 83

@ 25 °C

@ 25 °C

45 7

Time ( s)

t

P

tP =

=

2f

f

OSC

1

OSC

1

t

EN

for TNY253/254

for TNY255

PI-2248-090198

PI-2194-062398

Typical Performance Characteristics

BREAKDOWN vs. TEMPERATURE

1.1

1.0

(Normalized to 25 °C)

Breakdown Voltage (V)

0.9

-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

Figure 17. Current Limit Envelope.

PI-2213-040901

7/01

C

13

TNY253/254/255

1.2

1.0

0.8

0.6

0.4

0.2

0.0
0

160 320 480 640 800

di/dt in mA/µs

TNY255 CURRENT LIMIT vs. di/dt

PI-2234-082798

Current Limit

(Normalized to 80 mA/µs)

1.4

Typical Performance Characteristics (Continued)

CURRENT LIMIT vs. TEMPERATURE

1.4

1.2

1.0

0.8

0.6

Current Limit

0.4

(Normalized to 25 °C)

0.2

0.0

-50

-25 0 25 50 75 100 125

Junction Temperature (°C)

TNY254 CURRENT LIMIT vs. di/dt

1.4

1.2

µs)

1.0

0.8

PI-2236-033001

PI-2232-082798

TNY253 CURRENT LIMIT vs. di/dt

1.4

1.2

1.0

0.8

0.6

Current Limit

0.4

0.2

(Normalized to 12.5 mA/µs)

0.0
0 12.5 25 37.5 50 62.5 75 87.5 100

di/dt in mA/µs

PI-2230-082798

0.6

Current Limit

0.4

(Normalized to 25 mA/

0.2

0.0
0 50 100 150 200 250

di/dt in mA/µs

BYPASS PIN START-UP WAVEFORM

7
6
5
4

3
2
1

BYPASS Pin Voltage (V)

0

0 0.2 0.4 0.6 0.8 1.0

Time (ms)

PI-2240-082898

OUTPUT CHARACTERISTIC

300

T

=25 °C

250

200

150

100

Drain Current (mA)

50

0

0246810

CASE

=100 °C

T

CASE

Scaling Factors:
TNY253 1.00

TNY254 1.00
TNY255 1.33

DRAIN Voltage (V)

PI-2221-033001

C

14

7/01

Typical Performance Characteristics (Continued)

TNY253/254/255

C

vs. DRAIN VOLTAGE

OSS

100

Scaling Factors:

TNY253 1.00
TNY254 1.00
TNY255 1.33

10

DRAIN Capacitance (pF)

1

0 600

200 400

DRAIN Voltage (V)

PI-2223-033001

DRAIN CAPACITANCE POWER

50

Scaling Factors:

40

30

20

Power (mW)

10

0

TNY253 1.00
TNY254 1.00
TNY255 1.33

0 200 400 600

DRAIN Voltage (V)

PI-2225-033001

DIM

A
B
C
G
H

J1

J2

K

M
N
P
Q

Notes:

1. Package dimensions conform to JEDEC
specification MS-001-AB for standard dual in-line
(DIP) package .300 inch row spacing
(PLASTIC) 8 leads (issue B, 7/85).

2. Controlling dimensions are inches.

3. Dimensions shown do not include mold flash
or other protrusions. Mold flash or
protrusions shall not exceed .006 (.15) on any
side.

4. D, E and F are reference datums on the molded
body.

0.370-0.385

0.245-0.255

0.125-0.135

0.015-0.040

0.120-0.135

0.060 (NOM)

0.014-0.022

0.010-0.012

L

0.090-0.110

0.030 (MIN)

0.300-0.320

0.300-0.390

inches

0.300 BSC

mm

9.40-9.78

6.22-6.48

3.18-3.43

0.38-1.02

3.05-3.43

1.52 (NOM)

0.36-0.56

0.25-0.30

2.29-2.79

0.76 (MIN)

7.62-8.13

7.62-9.91

7.62 BSC

DIP-8

D S .004 (.10)

85

-E-

B

1

A

M

G

L

4

-D-

J1

C

N

-F-

H

J2

K

Q
P

P08A

PI-2076-040501

7/01

C

15

TNY253/254/255

SMD-8

-E-

B

J3

G08A

D S .004 (.10)

85

E S .010 (.25)

P

1

L

A

M

4

-D-

J1

C

-F-

J4

.010 (.25) M A S

J2

Heat Sink is 2 oz. Copper

As Big As Possible

.046

.060

Pin 1

.086

.186

Solder Pad Dimensions

.004 (.10)

α

G

.286

.060

DIM

G

.420

J1

.046

J2
J3

.080

J4

M

Notes:

1. Package dimensions conform to JEDEC

K

H

specification MS-001-AB (issue B, 7/85)
except for lead shape and size.

2. Controlling dimensions are inches.

3. Dimensions shown do not include mold
flash or other protrusions. Mold flash or
protrusions shall not exceed .006 (.15) on
any side.

4. D, E and F are reference datums on the
molded body.

A

0.370-0.385

B

0.245-0.255

C

0.125-0.135

0.004-0.012

H

0.036-0.044

0.060 (NOM)

0.048-0.053

0.032-0.037

0.007-0.011

K

0.010-0.012

L

0.030 (MIN)

P

0.372-0.388

α

inches

0.100 BSC

0-8°

mm

9.40-9.78

6.22-6.48

3.18-3.43

0.10-0.30

0.91-1.12

1.52 (NOM)

1.22-1.35

0.81-0.94

0.18-0.28

0.25-0.30

2.54 BSC

0.76 (MIN)

9.45-9.86
0-8°

PI-2077-042601

16

C
7/01

Notes

TNY253/254/255

7/01

C

17

TNY253/254/255

Notes

18

C
7/01

Notes

TNY253/254/255

7/01

C

19

TNY253/254/255

Revision

A
B

C

Notes

-

1) Leading edge blanking time (t

2) Minimum DRAIN supply current (I

) typical and minimum values increased to improve design flexibility.

LEB

, IS2) eliminated as it has no design revelance.

S1

1) Updated package reference.

2) Corrected VR1 in Figure 12.

3) Corrected storage temperature, θ

and θJC and updated nomenclature in parameter table.

JA

4) Corrected spacing and font sizes in figures.

Date
9/98
2/99

7/01

For the latest updates, visit our Web site: www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it
convey any license under its patent rights or the rights of others.

The PI Logo,

TOPSwitch, TinySwitch

and

EcoSmart

are registered trademarks of Power Integrations, Inc.

©Copyright 2001, Power Integrations, Inc.

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20

C
7/01