This product is not recommended for new designs.
TOP232-234
TOPSwitch-FX
Family
Design Flexible, EcoSmart, Integrated
Off-Line Switcher
Product Highlights
Lower System Cost, High Design Flexibility
•
Features eliminate or reduce cost of external components
•
Fully integrated soft-start for minimum stress/overshoot
•
Externally settable accurate current limit
•
Wider duty cycle for more power, smaller input capacitor
•
Line under-voltage (UV) detection: no turn off glitches
•
Line overvoltage (OV) shutdown extends line surge limit
•
Line feed-forward with maximum duty cycle (DC
MAX
)
reduction rejects ripple and limits DC
MAX
at high line
•
Single resistor sets OV/UV thresholds, DC
MAX
reduction
•
Frequency jittering reduces EMI and EMI filtering costs
•
Regulates to zero load without dummy loading
•
132 kHz frequency reduces transformer/power supply size
•
Half frequency option for video applications
•
Hysteretic thermal shutdown for automatic recovery
•
Large thermal hysteresis prevents PC board overheating
•
Standard packages with omitted pins for large creepage
•
Active-on and active-off remote ON/OFF capability
•
Synchronizable to a lower frequency
EcoSmart™– Energy Efficient
•
Cycle skipping reduces no-load consumption
•
Reduced consumption in remote off mode
•
Half frequency option for high efficiency standby
•
Allows shutdown/wake-up via LAN/input port
AC
IN
+
DC
OUT
-
D
M
CONTROL
C
TOPSwitch-FX
S
F
PI-2503-062515
Figure 1. Typical Flyback Application.
OUTPUT POWER TABLE
Product
3
230 VAC ±15%
Adapter
1
TOP232P
TOP232G
TOP232Y
TOP233P
TOP233G
TOP233Y
TOP234P
TOP234G
TOP234Y
9W
10 W
13 W
20 W
16 W
30 W
Open
Frame
2
15 W
25 W
25 W
50 W
30 W
75 W
85-265 VAC
Adapter
1
6.5 W
7W
9W
15 W
11 W
20 W
Open
Frame
2
10 W
15 W
15 W
30 W
20 W
45 W
Description
TOPSwitch™-FX uses the proven TOPSwitch topology and
cost effectively integrates many new functions that reduce
system cost and, at the same time, improve design flexibility,
performance and energy efficiency. Like TOPSwitch, the
high-voltage power MOSFET, PWM control, fault protection
and other control circuitry are all integrated onto a single
CMOS chip, but with two added terminals. The first one is a
MULTI-FUNCTION (M) pin, which implements programmable
line OV/UV shutdown and line feed-forward/DC
MAX
reduction
with line voltage. The same pin can be used instead to
externally set an accurate current limit. In either case, this pin
can also be used for remote ON/OFF or to synchronize the
oscillator to an external, lower frequency signal. The second
added terminal is the FREQUENCY (F) pin and is available only
in the Y package. This pin provides the half frequency option
when connected to CONTROL (C) instead of SOURCE (S).
The features on the new pins can be disabled by shorting
them to the SOURCE, which allows the device to operate in a
three terminal
TOPSwitch
mode, but with the following new
transparent features: soft-start, cycle skipping, 132 kHz
switching frequency, frequency jittering, wider DC
MAX
,
Table 1.
Notes:
1. Typical continuous power in a non-ventilated enclosed adapter measured at
50 ˚C ambient.
2. Maximum practical continuous power in an open frame design with adequate
heat sinking, measured at 50 ˚C ambient. See key applications section for
detailed conditions.
3. Packages: P: DIP-8B, G: SMD-8B, Y: TO-220-7B.
hysteretic thermal shutdown and larger creepage. In addition,
all critical parameters such as frequency, current limit, PWM
gain, etc. have tighter temperature and absolute tolerances
compared to the TOPSwitch-II family. Higher current limit
accuracy and larger DC
MAX
, when combined with other
features allow for a 10% to 15% higher power capability on the
TOPSwitch-FX devices compared to equivalent TOPSwitch-II
devices for the same input/output conditions.
www.power.com
June 2015
This Product is Covered by Patents and/or Pending Patent Applications.
TOP232-234
Section List
Pin Functional Description
....................................................................................................................................... 3
TOPSwitch-FX Family Functional Description
........................................................................................................ 4
CONTROL (C) Pin Operation .................................................................................................................................... 4
Oscillator and Switching Frequency.......................................................................................................................... 5
Pulse Width Modulator and Maximum Duty Cycle .................................................................................................... 5
Minimum Duty Cycle and Cycle Skipping ................................................................................................................. 6
Error Amplifier .......................................................................................................................................................... 6
On-chip Current Limit with External Programability ................................................................................................... 6
Line Undervoltage Detection (UV) ............................................................................................................................. 6
Line Overvoltage Shutdown (OV) .............................................................................................................................. 7
Line Feed-Forward with DC
MAX
Reduction ................................................................................................................ 7
Remote ON/OFF and Synchronization...................................................................................................................... 7
Soft-Start ................................................................................................................................................................. 8
Shutdown/Auto-Restart ........................................................................................................................................... 8
Hysteretic Over-Temperature Protection ................................................................................................................... 8
Bandgap Reference ................................................................................................................................................. 8
High-Voltage Bias Current Source ............................................................................................................................ 8
Using FREQUENCY and MULTI-FUNCTION Pins
.................................................................................................... 9
FREQUENCY (F) Pin Operation ................................................................................................................................ 9
MULTI-FUNCTION (M) Pin Operation........................................................................................................................ 9
Typical Uses of FREQUENCY (F) Pin
...................................................................................................................... 11
Typical Uses of MULTI-FUNCTION (M) Pin
............................................................................................................. 12
Application Examples
............................................................................................................................................. 14
A High Efficiency, 30 W, Universal Input Power Supply ........................................................................................... 14
35 W Multiple Output Power Supply....................................................................................................................... 15
17 W PC Standby Power Supply ........................................................................................................................... 16
Processor Controlled Supply Turn On/Off ............................................................................................................... 17
Key Application Considerations
.............................................................................................................................. 19
TOPSwitch-FX vs. TOPSwitch-ll ............................................................................................................................. 19
TOPSwitch-FX Design Considerations ................................................................................................................... 20
TOPSwitch-FX Selection .................................................................................................................................. 20
Input Capacitor ................................................................................................................................................ 20
Primary Clamp and Output Reflected Voltage V
OR
.......................................................................................... 20
Output Diode ................................................................................................................................................... 21
Soft-Start......................................................................................................................................................... 21
EMI ................................................................................................................................................................. 21
Transformer Design.......................................................................................................................................... 21
Standby Consumption ..................................................................................................................................... 23
TOPSwitch-FX Layout Considerations .................................................................................................................... 23
Primary Side Connections ............................................................................................................................... 23
Y-Capacitor ..................................................................................................................................................... 23
Heat Sinking .................................................................................................................................................... 23
Quick Design Checklist .......................................................................................................................................... 23
Design Tools .......................................................................................................................................................... 23
Product Specifications and Test Conditions
.......................................................................................................... 24
Typical Performance Characteristics
..................................................................................................................... 30
Package Outlines
.................................................................................................................................................... 34
2
Rev. C 06/15
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TOP232-234
CONTROL (C)
VC
0
DRAIN (D)
INTERNAL
SUPPLY
ZC
1
SHUNT REGULATOR/
ERROR AMPLIFIER
-
+
IFB
VI
(LIMIT)
+
5.8 V
4.8 V
-
SOFT START
5.8 V
INTERNAL UV
COMPARATOR
CURRENT
LIMIT
ADJUST
ON/OFF
∏
8
SHUTDOWN/
AUTO-RESTART
-
+
CURRENT LIMIT
COMPARATOR
VBG + VT
MULTI-
FUNCTION (M)
VBG
STOP
DCMAX
SOFT-
START
DMAX
CLOCK
HYSTERETIC
THERMAL
SHUTDOWN
CONTROLLED
TURN-ON
GATE DRIVER
OV/UV
LINE
SENSE
DCMAX
FREQUENCY (F)
(Y Package Only)
HALF
FREQUENCY SAW
-
+
PWM
COMPARATOR
S
R
Q
Q
OSCILLATOR WITH JITTER
LEADING
EDGE
BLANKING
RE
SOURCE (S)
PI-2535-062615
Figure 2. Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
High-voltage power MOSFET drain output. The internal
start-up bias current is drawn from this pin through a switched
high-voltage current source. Internal current limit sense point
for drain current.
CONTROL (C) Pin:
Error amplifier and feedback current input pin for duty cycle
control. Internal shunt regulator connection to provide internal
bias current during normal operation. It is also used as the
connection point for the supply bypass and auto-restart/
compensation capacitor.
MULTI-FUNCTION (M) Pin:
Input pin for OV, UV, line feed-forward with DC
MAX
reduction,
external set current limit, remote ON/OFF and synchronization.
A connection to SOURCE pin disables all functions on this pin
and makes TOPSwitch-FX operate in simple three terminal
mode (like TOPSwitch-II).
FREQUENCY (F) Pin: (Y package only)
Input pin for selecting switching frequency: 132 kHz if
connected to SOURCE pin and 66 kHz if connected to
CONTROL pin. The switching frequency is internally set for
132 kHz only operation in P and G packages.
SOURCE (S) Pin:
Output MOSFET source connection for high-voltage power
return. Primary side control circuit common and reference
point.
Tab Internally
Connected to SOURCE Pin
7D
5F
4S
3M
1C
Y Package (TO-220-7B)
M
1
S
2
S
3
C
4
8
S
7
S
5
D
P Package (DIP-8B)
G Package (SMD-8B)
Figure 3. Pin Configuration.
PI-2501-031901
3
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Rev. C 06/15
TOP232-234
TOPSwitch-FX Family Functional Description
Like TOPSwitch, TOPSwitch-FX 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 4.
In addition to the three terminal TOPSwitch features, such as
the high-voltage start-up, the cycle-by-cycle current limiting,
loop compensation circuitry, auto-restart, thermal shutdown,
etc., the TOPSwitch-FX 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.
Two terminals, FREQUENCY (available only in Y package) and
MULTI-FUNCTION, have been added to implement some of
the new functions. These terminals can be connected to the
SOURCE pin to operate the TOPSwitch-FX in a TOPSwitch-
like three terminal mode. However, even in this three terminal
mode, the TOPSwitch-FX offers many new transparent
features that do not require any external components:
1. A fully integrated 10 ms soft-start reduces peak currents
and voltages during start-up and practically eliminates
output overshoot in most applications.
2. DC
MAX
of 78% allows smaller input storage capacitor, lower
input voltage requirement and/or higher power capability.
3. Cycle skipping at minimum pulse width achieves regulation
and very low power consumption at no load.
4. Higher switching frequency of 132 kHz reduces the
transformer size with no noticeable impact on EMI or on
high line efficiency.
5. Frequency jittering reduces EMI.
6. Hysteretic over-temperature shutdown ensures automatic
recovery from thermal fault. Large hysteresis prevents circuit
board overheating.
7. Packages with omitted pins and lead forming provide large
DRAIN creepage distance.
8. Tighter absolute tolerances and smaller temperature vari-
ations on switching frequency, current limit and PWM gain.
The MULTI-FUNCTION pin is usually used for line sensing by
connecting a resistor from this pin to the rectified DC high-
voltage bus to implement line over-voltage (OV)/under-voltage
(UV) and line feed-forward with DC
MAX
reduction. In this mode,
the value of the resistor determines the OV/UV thresholds and
the DC
MAX
is reduced linearly starting from a line voltage above
the under-voltage threshold. In high efficiency applications, this
pin can be used in the external current limit mode instead, to
reduce the current limit externally (to a value close to the
operating peak current), by connecting the pin to SOURCE
through a resistor. The same pin can also be used as a
remote ON/OFF and a synchronization input in both modes.
Auto-restart
I
CD1
78
Duty Cycle (%)
I
B
Slope = PWM Gain
47
I
M
= 140
µA
I
M
< I
M(DC)
I = 190
µA
M
1.5
1.5 1.9
I
C
(mA)
5.5 5.9
PI-2504-072799
Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.
The FREQUENCY pin in the TO-220 package sets the
switching frequency to the default value of 132 kHz when
connected to SOURCE pin. A half frequency option can be
chosen by connecting this pin to CONTROL pin instead.
Leaving this pin open is not recommended.
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
C
is the supply voltage for the control circuitry
including the MOSFET gate driver. An external bypass
capacitor closely connected between the CONTROL and
SOURCE pins is required to supply the instantaneous gate
drive current. The total amount of capacitance connected to
this pin also sets the auto-restart timing as well as control loop
compensation.
When rectified DC high-voltage is applied to the DRAIN pin
during start-up, the MOSFET is initially off, and the CONTROL
pin capacitor is charged through a switched high-voltage
current source connected internally between the DRAIN and
CONTROL pins. When the CONTROL pin voltage V
C
reaches
approximately 5.8 V, the control circuitry is activated and the
soft-start begins. The soft-start circuit gradually increases the
duty cycle of the MOSFET from zero to the maximum value
over approximately 10 ms. If no external feedback/supply
current is fed into the CONTROL pin by the end of the
soft-start, the high-voltage current source is turned off and the
CONTROL pin will start discharging in response to the supply
current drawn by the control circuitry. If the power supply is
designed properly, and no fault condition such as open loop or
shorted output exists, the feedback loop will close, providing
external CONTROL pin current, before the CONTROL pin
voltage has had a chance to discharge to the lower threshold
voltage of approximately 4.8 V (internal supply under-voltage
lockout threshold). When the externally fed current charges the
CONTROL pin to the shunt regulator voltage of 5.8 V, current
4
Rev. C 06/15
www.power.com
TOP232-234
in excess of the consumption of the chip is shunted to
SOURCE through resistor R
E
as shown in Figure 2. This
current flowing through R
E
controls the duty cycle of the power
MOSFET to provide closed loop regulation. The shunt
regulator has a finite low output impedance Z
C
that sets the
gain of the error amplifier when used in a primary feedback
configuration. The dynamic impedance Z
C
of the CONTROL
pin together with the external CONTROL pin capacitance sets
the dominant pole for the control loop.
When a fault condition such as an open loop or shorted output
prevents the flow of an external current into the CONTROL pin,
the capacitor on the CONTROL pin discharges towards 4.8 V.
At 4.8 V auto-restart is activated which turns the output MOSFET
off and puts the control circuitry in a low current standby
mode. The high-voltage current source turns on and charges
the external capacitance again. A hysteretic internal supply
under-voltage comparator keeps V
C
within a window of
typically 4.8 to 5.8 V by turning the high-voltage current source
on and off as shown in Figure 5. The auto-restart circuit has a
divide-by-8 counter which prevents the output MOSFET from
turning on again until eight discharge/charge cycles have
elapsed. This is accomplished by enabling the output MOSFET
only when the divide-by-8 counter reaches full count (S7). The
counter effectively limits TOPSwitch-FX power dissipation by
reducing the auto-restart duty cycle to typically 4%. Auto-
restart mode continues until output voltage regulation is again
achieved through closure of the feedback loop.
Oscillator and Switching Frequency
The internal oscillator linearly charges and discharges an
internal capacitance between two voltage levels to create a
sawtooth waveform for the pulse width modulator. The
oscillator sets the pulse width modulator/current limit latch at
the beginning of each cycle.
The nominal switching frequency of 132 kHz was chosen to
minimize transformer size while keeping the fundamental EMI
frequency below 150 kHz. The FREQUENCY pin (available
only in TO-220 package), when shorted to the CONTROL pin,
lowers the switching frequency to 66 kHz (half frequency)
which may be preferable in some cases such as noise
sensitive video applications or a high efficiency standby mode.
Otherwise, the FREQUENCY pin should be connected to the
SOURCE pin for the default 132 kHz. Trimming of the current
reference improves oscillator frequency accuracy.
To further reduce the EMI level, the switching frequency is
jittered (frequency modulated) by approximately ±4 kHz at
250 Hz (typical) rate as shown in Figure 6. Figure 28 shows
the typical improvement of EMI measurements with frequency
jitter.
Pulse Width Modulator and Maximum Duty Cycle
The pulse width modulator implements voltage mode control
by driving the output MOSFET with a duty cycle inversely
proportional to the current into the CONTROL pin that is in
excess of the internal supply current of the chip (see Figure 4).
The excess current is the feedback error signal that appears
across R
E
(see Figure 2). This signal is filtered by an RC
network with a typical corner frequency of 7 kHz to reduce the
effect of switching noise in the chip supply current generated
~
~
~
~
V
UV
V
LINE
0V
S7
S0
S1
S2
S6
S7
S0
S1
S2
S6
S7
S0
S1
S2
S6
S7
S7
~
~
~
~
~
~
~
~
V
C
0V
5.8 V
4.8 V
~
~
~
~
~
~
~
~
V
DRAIN
0V
~
~
V
OUT
0V
~
~
~
~
~
~
1
2
3
2
4
PI-2545-082299
Note: S0 through S7 are the output states of the auto-restart counter
Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down .
5
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Rev. C 06/15
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