The STR-S5707 and STR-S5708 are specifically designed to meet
the requirement for increased integration and reliability in off-line quasi-
resonant flyback converters with indirect feedback. Each device
incorporates the primary control and proportional drive circuit with a
third-generation high-voltage bipolar switching transistor.
Crucial system parameters such as maximum ON time and OFF
time are fixed during manufacture. Local control circuit decoupling and
layout are optimized within each device.
Cycle-by-cycle current limiting, under-voltage lock-out with hyster-
esis, over-voltage protection, and thermal shutdown protect these
devices during all normal and overload conditions. Over-voltage
protection and thermal shutdown are latched after a short delay. A
primary-side error amplifier with reference is included to facilitate
regulation from an auxiliary or bias winding of the power transformer. A
versatile triple-level inhibit circuit includes the OFF time synchronization
required to establish quasi-resonant operation. The inhibit function has
also been expanded to initiate operation in stand-by mode in which the
power supply delivers a small fraction of the steady-state output power.
The dual requirements of dielectric isolation and low transient thermal
impedance and steady-state thermal resistance are satisfied in an over-
molded single-in-line power package.
Proven in substantial volumes, this device and its fixed-frequency
counterparts represents a significant advance in off-line SMPS reliability
growth and integration.
FEATURES
I Quasi-Resonant Operation for Low EMI and High Efficiency
I Low-Power Output Standby Mode
I Indirect Feedback from Auxiliary Winding
Reduces External Component Count
I Pulse-by-Pulse Over-Current Protection
I Latched Over-Voltage and Thermal Protection
I Third-Generation Switching Transistor with Proportional Drive
I Maximum ON Time and Off Time Set During Manufacture
I Internal Under-Voltage Lockout with Hysteresis
I Over-Molded SIP with Integral Isolated Heat Spreader
Always order by complete part number:
Part
Output Current
Output Power, P
O
Number
Continuous, I
C
Peak, I
CM
Wide AC In
220/240 VAC In
STR-S5707
6 A
12 A
90 W
140 W
STR-S5708
7.5 A
15 A
120 W
180 W
Data Sheet
28114A*
OFF-LINE SWITCHING REGULATORS
WITH BIPOLAR SWITCHING TRANSISTOR
+
OVER-CURRENT
PROTECTION
BASE
COLLECTOR
UVLO
COMMON
V IN
Dwg. PK-004
INHIBIT
FAULT
LATCH
REF.
1
2
3
4
5
6
7
OSC.
R
S
FAULT
8
9
SINK
DRIVE
+
DRIVE
32 V SENSE
+
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
IN
........................... 15 V
Output Voltage, V
CEX
....................... 850 V
V
EBO
................................................ 7 V
Continuous Output Current,
I
C
.......................................... See Table
1 ms Single-Pulse Output Current,
I
CM
........................................ See Table
Sink Current, I
S
................................. 1.5 A
Drive Current, I
D
.......................... -700 mA
Inhibit Voltage, V
INH
........................... 15 V
Over-Current Protection Voltage Range,
V
OCP
............................................
3.5 V
Insulation Voltage,V
WM(RMS)
........... 2000 V
Package Power Diss., P
D
........ See Graph
Output Junction Temperature, T
J
.. +150
C
Internal Frame Temperature, T
F
... +125
C
Operating Temperature Range,
T
A
............................... -20
C to +125
C
Storage Temperature Range,
T
stg
............................. -40
C to +125
C
TM
STR-S5707
AND
STR-S5708
STR-S5707
AND
STR-S5708
OFF-LINE
QUASI-RESONANT FLYBACK
SWITCHING REGULATORS
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
TM
FUNCTIONAL BLOCK DIAGRAM
ALLOWABLE PACKAGE POWER DISSIPATION
MAXIMUM SAFE OPERATING AREA
60
40
20
20
60
100
3.2 W
140
LIMITED BY FRAME
TEMP. = +125
C MAX.
RECOMMENDED MAX.
FRAME TEMP. = +100
C
FREE AIR
54 W
0
TEMPERATURE in
C
ALLOWABLE PACKAGE POWER DISSIPATION in WATTS
MOUNTING SURFACE
TEMPERATURE
Dwg. GK-003-2
PROPORTIONAL
DRIVE
TSD
OVER-VOLT.
PROTECT
OSC.
R
S
Q
V
IN
SENSE
7
OVER-CURRENT
PROTECTION
COMMON
COLLECTOR
BASE
SINK
DRIVE
3300 pF
1 k
Rton
Rtoff
0.75 V
-1 V
1.4 V
5.1 V
REF.
FAULT
LATCH
+
+
+
+
INHIBIT
9
6
8
4
3
1
2
5
Dwg. FK-001-1
UVLO
1500 pF
30
3.0
0.3
COLLECTOR-EMITTER VOLTAGE in VOLTS
COLLECTOR CURRENT in AMPERES
Dwg. GK-002-1A
1.0
10
0
200
400
600
1000
0.5
5.0
800
STR-S5708 (15 A)
STR-S5707 (12 A)
L = 6 mH
I
B1
= 2.5 A
I
B2
= 0.8 A
t
on
= 100
s
dc < 1%
Copyright 1994 Allegro MicroSystems, Inc.
www.allegromicro.com
STR-S5707
AND
STR-S5708
OFF-LINE
QUASI-RESONANT FLYBACK
SWITCHING REGULATORS
ELECTRICAL CHARACTERISTICS at T
A
= +25
C, V
IN
= 8.5 V, voltage measurements are refer-
enced to Common (pin 2) (unless otherwise noted).
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ. Max.
Units
On-State Voltage
V
INT
Turn-on, increasing V
IN
7.6
8.0
8.4
V
Under-Voltage Lockout
V
INQ
Turn-off, decreasing V
IN
4.6
4.9
5.2
V
Over-Voltage Threshold
V
OVP(th)
9.2
10.7
V
Output Leakage Current
I
CEX
V
CE
= 850 V, V
BE
= -1.5 V
100
A
Output Saturation Voltage
V
CE(sat)
STR-S5707, I
C
= 2 A, I
B
= 400 mA
400
mV
STR-S5708, I
C
= 3 A, I
B
= 600 mA
400
mV
V
BE(sat)
STR-S5707, I
C
= 2 A, I
B
= 400 mA
1.5
V
STR-S5708, I
C
= 3 A, I
B
= 600 mA
1.5
V
DC Current Gain
h
FE
V
CE
= 4 V, I
C
= 1 A
29
61
Maximum ON Time
t
on
33
41
s
Minimum OFF Time
t
off
45
55
s
Over-Current Threshold
V
OCP(th)
-0.88
-1.0
-1.12
V
Sense Voltage
V
SENSE
I
SENSE
= 3.2 mA
31.7
32.0
32.3
V
Inhibit Threshold Voltage
V
INH(th)
Oscillation stops
0.65
0.75
0.85
V
Oscillation synchronized
1.4
2.0
V
Oscillation stops (fault latch set)
3.2
5.1
5.8
V
Latch Holding Current
I
INH
V
IN
reduced from 10.7 V to 4 V
500
A
Latch Reset Voltage
V
Q
I
IN
100 A, V
IN
reduced from 10.7 V
2.5
3.1
V
Ref. Voltage Temp. Coeff.
VZ
-20
C T
F
+100C, I
IN
= 3.2 mA
2.5
mV/
C
Supply Current
I
IN(ON)
Operating
15
28
mA
I
IN(OFF)
200
A
Insulation RMS Voltage
V
WM(RMS)
All terminals simultaneous reference
2000
V
metal plate against backside
Thermal Shutdown
T
J
125
150
C
Thermal Resistance
R
JM
Output junction to mounting surface
2.0
C/W
NOTES: Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.
www.allegromicro.com
STR-S5707
AND
STR-S5708
OFF-LINE
QUASI-RESONANT FLYBACK
SWITCHING REGULATORS
TYPICAL QUASI-RESONANT FLYBACK CONVERTER
WARNING: lethal potentials are present. See below.
APPLICATIONS INFORMATION
WARNING --
These devices are designed to be operated at lethal voltages and energy levels.
Circuit designs that embody these components must conform with applicable safety requirements.
Precautions must be taken to prevent accidental contact with power-line potentials.
Do not connect grounded test equipment.
The use of an isolation transformer is recommended during circuit development and breadboarding.
Recommended mounting hardware torque:
4.34 5.79 lbfft (6 8 kgcm or 0.588 0.784 Nm).
Recommended metal-oxide-filled, alkyl-degenerated oil base, silicone grease:
Dow Corning 340, or equivalent
FULL-BRIDGE
RECTIFIER
AC INPUT
+
+
+ OUTPUT
OUTPUT
+
Dwg. EK-005A
+
+
R
S
Q
7
+
+
+
+
9
6
8
4
3
1
2
5
#
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