POWERINT TNY255G

®
TNY253/254/255
®
TinySwitch Family
Energy Efficient, Low Power Off-line Switchers
Product Highlights
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
+
+
DC Output
–
Wide-Range
HV DC Input
D
TinySwitch
EN
BP
S
–
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
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
PI-2178-022699
Figure 1. Typical Standby Application.
TinySwitch SELECTION GUIDE
ORDER
PART
NUMBER
Recommended Range
for Lowest System Cost*
PACKAGE
TNY253P
DIP-8
TNY253G
SMD-8
TNY254P
DIP-8
TNY254G
SMD-8
TNY255P
DIP-8
TNY255G
SMD-8
230 VAC or
115 VAC
w/Doubler
85-265
VAC
0-4 W
0-2 W
2-5 W
1-4 W
4-10 W
3.5-6.5 W
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
REGULATOR
5.8 V
BYPASS
DRAIN
UNDER-VOLTAGE
50 µA
OSCILLATOR
5.8 V
5.1 V
+
+
-
-
VI
LIMIT
CLOCK
DCMAX
THERMAL
SHUTDOWN
S
Q
R
Q
LEADING
EDGE
BLANKING
1.5 V + VTH
SOURCE
ENABLE
PI-2197-061898
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.
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
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
(Pulse Width Modulator) controller, the TinySwitch uses a
simple ON/OFF control to regulate the output voltage.
The TinySwitch controller consists of an Oscillator, Enable
(Sense and Logic) circuit, 5.8V Regulator, Under-Voltage
2
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7/01
BYPASS 1
8
SOURCE
SOURCE 2
7
SOURCE
SOURCE 3
6
SOURCE
ENABLE 4
5
DRAIN
P Package (DIP-8)
G Package (SMD-8)
PI-2199-031501
Figure 3. Pin Configuration.
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 (DMAX) which runs at typically 67% duty
cycle and the Clock signal that indicates the beginning of each
cycle. When cycles are skipped (see below), the oscillator
frequency doubles (except for TNY255 which remains at
130kHz). This increases the sampling rate at the ENABLE pin
for faster loop response.
Enable (Sense and Logic)
The ENABLE pin circuit has a source follower input stage set
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
(ILIMIT), the power MOSFET is turned off for the remainder of
that cycle.
The leading edge blanking circuit inhibits the current limit
comparator for a short time (tLEB) after the power MOSFET is
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 DCMAX by the oscillator.
Since the current limit and frequency of a given TinySwitch
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 DCMAX limit is reached.
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.
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
7/01
3
TNY253/254/255
V
EN
V
EN
CLOCK
CLOCK
DC
DC
MAX
MAX
I DRAIN
I DRAIN
V DRAIN
V DRAIN
PI-2259-061298
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.
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
line ripple rejection and relatively constant power delivery
independent of the input voltage.
The response time of TinySwitch ON/OFF control scheme is
very fast compared to normal PWM control. This provides high
line ripple rejection and excellent transient response.
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).
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
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44 kHz Switching Frequency (TNY253/254)
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 diodeZener 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).
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.
PI—2253-062398
TNY253/254/255
V
EN
CLOCK
DC
V
IN
0V
MAX
I DRAIN
VDRAIN
0V
0
.2
.4
.6
.8
1
Time (ms)
V DRAIN
PI-2261-061198
PI—2251-062398
Figure 7. TinySwitch Power-Up Timing Diagram.
V
IN
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.
12 V
0V
VDRAIN
BYPASS Pin Capacitor
The BYPASS pin uses a small 0.1 µF ceramic capacitor for
decoupling the internal power supply of the TinySwitch.
Application Examples
12 V
0V
0
100
200
300
400
500
Time (ms)
Television Standby
Figure 8. TinySwitch Power Down Timing Diagram.
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
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
7/01
5
TNY253/254/255
1
+
T1
D1
1N4934
L1
15 µH
10
C4
330 µF
10 V
8
4
Optional
DC IN
120-375 VDC
C1
0.01 µF
1 kV
R1
100 Ω
1/2 W
D
U1
TNY253P
C5
47 µF
10 V
TinySwitch
EN
RTN
U2
SFH615-2
BP
R2
1 kΩ
S
C3
0.1 µF
C2
56 pF
1 kV
+ 7.5 V
VR1
1N5235B
–
C6
680 pF
Y1 Safety
PI-2246-082898
Figure 9. 1.3 W TV Stand-by Circuit using TNY253.
1
R1
150 kΩ
1W
240-375
VDC
C1
0.01 µF
1 kV
D2
SB540
L1
10 µH
10
C2
4700 pF
1 kV
C4
2700 µF
6.3 V
4
D1
1N4937
Optional
T1
D
U1
TNY255P
8
+5V
RTN
TinySwitch
EN
BP
S
C5
220 µF
10 V
R2
68 Ω
U2
LTV817
C3
0.1 µF
VR1
1N5229B
PI-2242-082898
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
6
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7/01
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
1
R2
100 kΩ
1W
D1
D2
1N4005 1N4005
L2
3.3 µH
D5
FR201
T1
10
C4
2200 pF
C5
220 µF
25 V
5
2
D6
1N4937 D TinySwitch
85-265
VAC RF1
C1
6.8 µF
400 V
10 Ω
U2
LTV817
BP
S
C2
4.7 µF
400 V
D3
D4
1N4005 1N4005
R7
100 Ω
R9
47 Ω
Fusible
C3
0.1 µF
R1
1.2 kΩ
L1
560 µH
RTN
R8
820 Ω
EN
U1
TNY254P
+ 5.2 V
C6
220 µF
16 V
Q1
2N3904
R3
22 Ω
R5
18 Ω
1/8 W
R4
1Ω
1W
C8
2.2 nF
Y1 Safety
VR1
1N5230B
4.7 V
R6
0.82 Ω
1/2 W
PI-2244-082898
Figure 11. 3.6 W Constant Voltage-Constant Current Cellular Phone Charger Circuit.
1
T1
D3
1N3934
10
C6
100 µF
16V
D1
1N4004
5
C1
2.2 µF
200 V
115 VAC
± 15%
RF1
1.8 Ω
D2
1N4004
C2
2.2 µF
200 V
D
C4
68 pF
1 KV
U1
TNY253P
R2
100 Ω
6
+9V
VR1
1N5239B
RTN
TinySwitch
EN
BP
S
C3
0.1 µF
C5
2.2 nF
Y1 Safety
Fusible
PI-2190-031501
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
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
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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 VBE
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.
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.
8
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Key Application Considerations
For the most up to date information visit our Web site
at: www.powerint.com
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.
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 (ILIMIT)
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
TNY253/254/255
Safety Spacing
Input Filter Capacitor
Output Filter Capacitor
Transformer
+
HV
SEC
PRI
–
S
D
TOP VIEW
Y1Capacitor
TinySwitch
CBP
Optocoupler
BP
S
EN
–
DC +
Out
Maximize hatched copper
areas (
) for optimum
heat sinking
PI-2176-071398
Figure 13. Recommended PC Layout for the TinySwitch.
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.
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.
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.
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.
C
7/01
9
TNY253/254/255
ABSOLUTE MAXIMUM RATINGS(1)
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
Storage Temperature ..................................... -65 to 150 °C
Operating Junction Temperature(2) ................ -40 to 150 °C
Lead Temperature(3) ................................................ 260 °C
Thermal Impedance (θJA) ................ 45 °C/W(4), 35 °C/W(5)
Thermal Impedance (θJC) ..................................... 11 °C/W
1. All voltages referenced to SOURCE, TA = 25 °C.
2. Normally limited by internal circuitry.
3. 1/16" from case for 5 seconds.
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.
Parameter
Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
Min
Typ
Max
40
44
48
115
130
140
66
68
71
64
67
69
TJ = -40 °C to 125 °C
-68
-50
-30
TJ = 125 °C
-68
-52
-45
See Figure 14
(Unless Otherwise Specified)
Units
CONTROL FUNCTIONS
Output
Frequency
fOSC
Maximum
Duty Cycle
DCMAX
TJ = 25 °C
S1 Open
TNY253
TNY254
TNY255
TNY253
TNY254
TNY255
kHz
%
ENABLE Pin Turnoff
Threshold Current
IDIS
ENABLE Pin
Hysteresis Current
IHYS
See Note A
-15
-10
-5
µA
ENABLE Pin
Voltage
VEN
IEN = -25 µA
1.10
1.45
1.80
V
ENABLE ShortCircuit Current
IENSC
VEN = 0 V, TJ = -40 °C to 125 °C
-58
-42
-25
VEN = 0 V, TJ = 125 °C
VEN = 0 V
TNY253
TNY254
(MOSFET Not Switching)
TNY255
See Note B
TNY253
ENABLE Open
TNY254
(MOSFET Switching)
See Note B, C
TNY255
TNY253
VBP = 0 V, TJ = 25 °C
TNY254
See Note D, E
TNY255
TNY253
VBP = 4 V, TJ = 25 °C
TNY254
See Note D, E
TNY255
-58
-45
-38
160
200
170
215
140
180
215
265
-5.0
-3.5
-2.0
-6.0
-4.5
-3.0
-4.0
-2.5
-1.0
-4.8
-3.3
-1.8
5.6
5.8
6.1
V
0.60
0.72
0.85
V
IS1
DRAIN
Supply Current
IS2
ICH1
BYPASS Pin
Charge Current
BYPASS Pin
Voltage
BYPASS
Hysteresis
10
C
7/01
ICH2
VBP
VBPH
See Note D
µA
µA
µA
µA
mA
mA
TNY253/254/255
Conditions
Parameter
Symbol
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 14
(Unless Otherwise Specified)
Min
Typ
Max
Units
CIRCUIT PROTECTION
Current Limit
di/dt = 12.5 mA/µs
TJ = 25 °C
TNY253
135
150
165
ILIMIT
di/dt = 25 mA/µs
TJ = 25 °C
TNY254
230
255
280
Note F
di/dt = 80 mA/µs
TJ = 25 °C
TNY255
255
280
310
See Figure 17
TJ = 25 °C
Initial Current
Limit
IINIT
Leading Edge
Blanking Time
tLEB
TJ = 25 °C
Current Limit
Delay
tILD
TJ = 25 °C
See Note G
0.65 x
ILIMIT(MIN)
TNY253
TNY254
TNY255
TNY253
TNY254
TNY255
Thermal Shutdown
Temperature
mA
170
240
170
215
125
Thermal Shutdown
Hysteresis
mA
ns
200
250
100
150
135
145
ns
°C
°C
70
OUTPUT
ON-State
Resistance
RDS(ON)
OFF-State
Leakage
IDSS
Breakdown
Voltage
BVDSS
Rise Time
Fall Time
TNY253/TNY254
ID = 25 mA
TNY255
ID = 33 mA
TJ = 25 °C
31
36
TJ = 100 °C
50
60
TJ = 25 °C
23
27
TJ = 100 °C
37
45
VBP = 6.2 V, VEN = 0 V,
VBP = 6.2 V, VEN = 0 V,
IDS = 100 µA, TJ = 25 °C
tR
Measured with Figure 10
Schematic.
tF
50
VDS = 560 V, TJ = 125 °C
Ω
µA
V
700
50
ns
50
ns
C
7/01
11
TNY253/254/255
Conditions
Parameter
Symbol
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 14
(Unless Otherwise Specified)
Min
Max
Typ
Units
OUTPUT (cont.)
DRAIN Supply
Voltage
50
Output Enable
Delay
tEN
Output Disable
Setup Time
tDST
V
TNY253
TNY254
TNY255
See Figure 16
14
µs
10
µs
0.5
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 IDSS when ENABLE pin is shorted to ground (MOSFET not switching)
and the sum of IS2 and IDSS when ENABLE pin is open (MOSFET switching).
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.
G. This parameter is derived from the change in current limit measured at 5X and 10X of the di/dt shown in the ILIMIT
specification.
470 Ω
5W
S2
470 Ω
D
S
EN
S
S
S
S
BP
S1
50 V
10 V
0.1 µF
NOTE: This test circuit is not applicable for current limit or output characteristic measurements.
PI-2211-061898
Figure 14. TinySwitch General Test Circuit.
12
C
7/01
TNY253/254/255
DCMAX
t2
tP
t1
HV 90%
90%
DRAIN
VOLTAGE
ENABLE
tEN
t
D= 1
t2
1
t =
for TNY253/254
P 2f
OSC
10%
0V
tP =
PI-2048-033001
PI-2194-062398
Figure 16. TinySwitch Output Enable Timing.
PI-2248-090198
DRAIN Current (normalized)
Figure 15. TinySwitch Duty Cycle Measurement.
1
for TNY255
fOSC
tLEB (Blanking Time)
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
IINIT(MIN)
ILIMIT(MAX) @ 25 °C
ILIMIT(MIN) @ 25 °C
0
0
1
2
3
4
5
6
7
8
Time ( s)
Figure 17. Current Limit Envelope.
Typical Performance Characteristics
BREAKDOWN vs. TEMPERATURE
FREQUENCY vs. TEMPERATURE
1.0
PI-2238-033001
1.2
Output Frequency
(Normalized to 25 °C)
PI-2213-040901
Breakdown Voltage (V)
(Normalized to 25 °C)
1.1
1.0
0.8
0.6
0.4
0.2
0.9
0
-50 -25
0
25
50
75 100 125 150
Junction Temperature (°C)
-50
-25
0
25
50
75
100 125
Junction Temperature (°C)
C
7/01
13
TNY253/254/255
Typical Performance Characteristics (Continued)
TNY253 CURRENT LIMIT vs. di/dt
CURRENT LIMIT vs. TEMPERATURE
1.0
0.8
0.6
0.4
0.2
0.0
PI-2230-082798
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-50 -25
0
25
50
75
100 125
0 12.5 25 37.5 50 62.5 75 87.5 100
Junction Temperature (°C)
di/dt in mA/µs
TNY254 CURRENT LIMIT vs. di/dt
1.0
0.8
0.6
0.4
0.2
0.0
PI-2234-082798
1.2
TNY255 CURRENT LIMIT vs. di/dt
1.4
Current Limit
(Normalized to 80 mA/µs)
PI-2232-082798
Current Limit
(Normalized to 25 mA/µs)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
50
100
150
200
250
0
160
di/dt in mA/µs
480
640
800
OUTPUT CHARACTERISTIC
BYPASS PIN START-UP WAVEFORM
6
5
4
3
2
1
300
TCASE=25 °C
TCASE=100 °C
250
Drain Current (mA)
PI-2240-082898
7
BYPASS Pin Voltage (V)
320
di/dt in mA/µs
PI-2221-033001
Current Limit
(Normalized to 25 °C)
1.2
1.4
Current Limit
(Normalized to 12.5 mA/µs)
PI-2236-033001
1.4
200
150
100
Scaling Factors:
TNY253 1.00
TNY254 1.00
TNY255 1.33
50
0
0
0
0.2
0.4
0.6
Time (ms)
14
C
7/01
0.8
1.0
0
2
4
6
DRAIN Voltage (V)
8
10
TNY253/254/255
Typical Performance Characteristics (Continued)
COSS vs. DRAIN VOLTAGE
DRAIN CAPACITANCE POWER
PI-2223-033001
50
Scaling Factors:
TNY253 1.00
TNY254 1.00
TNY255 1.33
40
10
PI-2225-033001
Scaling Factors:
TNY253 1.00
TNY254 1.00
TNY255 1.33
Power (mW)
DRAIN Capacitance (pF)
100
30
20
10
1
0
200
400
0
600
0
200
DRAIN Voltage (V)
400
600
DRAIN Voltage (V)
DIP-8
DIM
inches
D S .004 (.10)
mm
8
A
B
0.370-0.385
0.245-0.255
9.40-9.78
6.22-6.48
C
G
H
J1
J2
K
0.125-0.135
0.015-0.040
0.120-0.135
0.060 (NOM)
0.014-0.022
0.010-0.012
3.18-3.43
0.38-1.02
3.05-3.43
1.52 (NOM)
0.36-0.56
0.25-0.30
L
M
N
P
Q
0.090-0.110
0.030 (MIN)
0.300-0.320
0.300-0.390
0.300 BSC
2.29-2.79
0.76 (MIN)
7.62-8.13
7.62-9.91
7.62 BSC
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
G
or other protrusions. Mold flash or
protrusions shall not exceed .006 (.15) on any
side.
L
4. D, E and F are reference datums on the molded
body.
5
-E-
B
1
4
-D-
A
M
J1
N
C
-FH
J2
K
Q
P
P08A
PI-2076-040501
C
7/01
15
TNY253/254/255
SMD-8
Heat Sink is 2 oz. Copper
As Big As Possible
D S .004 (.10)
8
-E-
1
E S .010 (.25)
P
B
.420
.046 .060
.080
.086
.186
.286
-D-
A
M
.060 .046
Pin 1
4
L
Solder Pad Dimensions
J1
C
K
-F.004 (.10)
J3
J4
G08A
DIM
inches
mm
A
B
C
G
H
J1
J2
J3
J4
K
L
M
P
α
0.370-0.385
0.245-0.255
0.125-0.135
0.004-0.012
0.036-0.044
0.060 (NOM)
0.048-0.053
0.032-0.037
0.007-0.011
0.010-0.012
0.100 BSC
0.030 (MIN)
0.372-0.388
0-8°
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°
5
J2
.010 (.25) M A S
α
G
H
Notes:
1. Package dimensions conform to JEDEC
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.
PI-2077-042601
16
C
7/01
TNY253/254/255
Notes
C
7/01
17
TNY253/254/255
Notes
18
C
7/01
TNY253/254/255
Notes
C
7/01
19
TNY253/254/255
Revision Notes
A
B
1) Leading edge blanking time (tLEB) typical and minimum values increased to improve design flexibility.
2) Minimum DRAIN supply current (IS1, IS2) eliminated as it has no design revelance.
C
Date
9/98
2/99
7/01
1) Updated package reference.
2) Corrected VR1 in Figure 12.
3) Corrected storage temperature, θJA and θJC and updated nomenclature in parameter table.
4) Corrected spacing and font sizes in figures.
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
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