Page 1
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
∞ ∞
∞ Garden Grove, CA 92841
1 (714) 898-8121
∞∞
∞∞
∞ FAX: (714) 893-2570
SG1526B/SG2526B/SG3526B
DESCRIPTION
The SG1526B is a high-performance pulse width modulator for switching
power supplies which offers improved functional and electrical characteristics over the industry-standard SG1526. A direct pin-for-pin replacement for
the earlier device with all its features, it incorporates the following enhancements: a bandgap reference circuit for improved regulation and drift
characteristics, improved undervoltage lockout, lower temperature coefficients on oscillator frequency and current-sense threshold, tighter tolerance on softstart time, much faster SHUTDOWN response, improved
double-pulse supperession logic for higher speed operation, and an improved output driver design with low shoot-through current, and faster rise
and fall times. This versatile device can be used to implement single-ended
or push-pull switching regulators of either polarity, both transformer-less
and transformer-coupled. The SG1526B is specified for operation over the
full military ambient temperature range of -55°C to 150°C. The SG2526B
is characterized for the industrial range of -25°C to 150°C, and the SG3526B
is designed for the commercial range of 0°C to 125°C.
REGULATING PULSE WIDTH MODULATOR
BLOCK DIAGRAM
+V
IN
METERING
F/F
TOGGLE
F/F
MEMORY
F/F
R
D
R
T
C
T
GROUND
Oscillator
Reference
Regulator
Undervoltage
Lockout
Soft
Start
RESET
C
SOFTSTART
COMPENSATION
+ ERROR
— ERROR
+ C.S.
— C.S.
SHUTDOWN
Q
Q
Q
Q
OUTPUT B
+V
C
OUTPUT A
+V
IN
FEATURES
••
••
• 8 to 35 volt operation
••
••
• 5V low drift 1% bandgap reference
••
••
• 1Hz to 500KHz oscillator range
••
••
• Dual 100mA source/sink
••
••
• Digital current limiting
••
••
• Double pulse suppression
••
••
• Programmable deadtime
••
••
• Improved undervoltage lockout
••
••
• Single pulse metering
••
••
• Programmable soft-start
••
••
• Wide current limit common mode range
••
••
• TTL/CMOS compatible logic ports
••
••
• Symmetry correction capability
••
••
• Guaranteed 6 unit synchronization
••
••
• Shoot thru currents less than 100mA
••
••
• Improved shutdown delay
••
••
• Improved rise and fall time
HIGH RELIABILITY FEATURES - SG1526B
♦♦
♦♦
♦ Available to MIL-STD-883
♦♦
♦♦
♦ MIL-M38510/12603BVA - JAN1526BJ
♦♦
♦♦
♦ Radiation data available
♦♦
♦♦
♦ LMI level "S" processing available
Amp
V
REF
To Internal
Circuitry
SYNC
S
R
D
S
T
Q
Page 2
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
∞ ∞
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SG1526B/SG2526B/SG3526B
ABSOLUTE MAXIMUM RATINGS (Note 1) (Note 1)
40V
40V
-0.3V to 5.5V
-0.3V to V
IN
200mA
50mA
Input Voltage (V
IN
) ...............................................................
Collector Supply Voltage (V
C
) .............................................
Logic Inputs .........................................................
Analog Inputs ..........................................................
Source/Sink Load Current (each output) .......................
Reference Load Current ..................................................
Logic Sink Current ...........................................................
Operating Junction Temperature
Hermetic (J, L Packages) .............................................
Plastic (N, DW Packages) ............................................
Storage Temperature Range ............................
Lead Temperature (Soldering, 10 Seconds) ...................
15mA
150°C
150°C
-65°C to 150°C
300°C
Note 1. Exceeding these ratings could cause damage to the device.
THERMAL DATA
J Package:
Thermal Resistance-
Junction to Case, θ
JC
.................. 25°C/W
Thermal Resistance-
Junction to Ambient, θ
JA
.............. 70°C/W
N Package:
Thermal Resistance-
Junction to Case, θ
JC
.................. 30°C/W
Thermal Resistance-
Junction to Ambient, θ
JA
............. 60°C/W
DW Package:
Thermal Resistance-
Junction to Case, θ
JC
.................. 35°C/W
Thermal Resistance-
Junction to Ambient, θ
JA
............. 90°C/W
L Package:
Thermal Resistance-
Junction to Case, θ
JC
................... 35°C/W
Thermal Resistance-
Junction to Ambient, θ
JA
........... 120°C/W
Note A. Junction Temperature Calculation: TJ = TA + (PD x θJA).
Note B. The above numbers for
θJC are maximums for the limiting
thermal resistance of the package in a standard mounting configuration. The θ
JA
numbers are meant to be
guidelines for the thermal performance of the device/pcboard system. All of the above assume no ambient
airflow.
RECOMMENDED OPERATING CONDITIONS (Note 2)
Input Voltage .............................................................
Collector Supply Voltage ........................................
Sink/Source Load Current (each output) ................
Reference Load Current ...........................................
Oscillator Frequency Range ..............................
Oscillator Timing Resistor ..................................
8V to 35V
4.5V to 35V
0 to 100mA
0 to 20mA
1Hz to 500KHz
2KΩ to 150KΩ
Oscillator Timing Capacitor ...............................
Available Deadtime Range at 40KHz ......................
Operating Junction Temperature Range:
SG1526B .......................................................
SG2526B .........................................................
SG3526B ............................................................
470pF to 20µF
5% to 50%
-55°C to 125°C
-25°C to 85°C
0°C to 70°C
Note 2. Range over which the device is functional.
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG1526B with -55°C ≤ TA ≤ 125°C, SG2526B with
-25°C ≤ T
A
≤ 85°C, SG3526B with 0°C ≤ TA ≤ 70°C, and VIN = 15V. Low duty cycle pulse testing techniques are used which maintains junction and
case temperatures equal to the ambient temperature.)
Reference Section (Note 3)
TJ = 25°C
V
IN
= 8 to 35V
I
L
= 0 to 20mA
Over Operating T
J
V
REF
= 0V
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
(Note 9)
Total Output Voltage Range (Note 9)
Short Circuit Current
SG3526B
Units
Undervoltage Lockout Section
V
REF
= 3.8V
V
REF
= 4.8V
RESET Output Voltage
RESET Output Voltage
Parameter Test Conditions
4.95
4.90
25
5.00
7
10
15
5.00
50
SG1526B/2526B
2.4
0.2
4.8
0.4
Min. Typ. Max. Min. Typ. Max.
5.05
10
20
50
5.10
125
4.90
4.85
25
5.00
10
10
15
5.00
50
5.10
20
25
50
5.15
125
V
mV
mV
mV
V
mA
2.4
0.2
4.8
0.4 V
V
Page 3
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
∞ ∞
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∞∞
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SG1526B/SG2526B/SG3526B
RS ≤ 50Ω mV
µA
ns
I
SOURCE
= 40µA
I
SINK
= 3.6mA
V
IH
= 2.4V
V
IL
= 0.4V
(Note9)
2.42.4 4
0.2
-125
-225
0.4
-200
-360
200
4
0.2
-125
-225
0.4
-200
-360
200
V
V
µA
µA
ns
Minimum Duty Cycle
Maximum Duty Cycle
V
COMPENSATION
= 0.4V
V
COMPENSATION
= 3.6V 45 49
0
45 49
0%
%
I
SOURCE
= 20mA
I
SOURCE
= 100mA
I
SINK
= 20mA
I
SINK
= 100mA
V
C
= 40V
C
L
= 1000pF
C
L
= 1000pF
HIGH Output Voltage
LOW Output Voltage
Collector Leakage
Rise Time
Fall Time
RS ≤ 2KΩ
R
L
≥ 10MΩ
V
PIN1
- V
PIN2
≥ 150mV, I
SOURCE
= 100µA
V
PIN2
- V
PIN1
≥ 150mV, I
SINK
= 100µA
R
S
≤ 2KΩ
V
IN
= 8V to 35V
Error Amplifier Section (Note 5)
Input Offset Voltage
Input Bias Current
Input Offset Current
DC Open Loop Gain
High Output Voltage
Low Output Voltage
Common Mode Rejection
Supply Voltage Rejection
Oscillator Section (Note 4)
TJ = 25°C
V
IN
= 8 to 35V
Over Operating T
J
RT = 150KΩ, CT = 20µF
R
T
= 2KΩ, CT = 470pF
V
IN
= 35V
V
IN
= 8V
R
L
= 2.0KΩ to V
REF
Initial Accuracy
Voltage Stability
Temperature Stability
(Note 9)
Minimum Frequency (Note 9)
Maximum Frequency
Sawtooth Peak Voltage
Sawtooth Valley Voltage
SYNC Pulse Width
SG3526B
Test ConditionsParameter Units
RESET = 0.4V
RESET = 2.4V
Error Clamp Voltage
C
S
Charging Current
ELECTRICAL CHARACTERISTICS (continued)
Soft-Start Section
Note 3. IL = 0mA
Note 4. F
OSC
= 40KHz (RT = 4.12KΩ ±1%, CT = .01µF ±1%, RD = 0Ω)
Note 5. VCM = 0 to 5.2V
Note 6. V
CM
= 0 to 12V
Note 7. VC = 15V
Note 8. V
IN
= 35V
Note 9. These parameters, although guaranteed over the recom-
mended operating conditions, are not tested in production.
Standby Current
0.3
2
150
0.4
0.15
5
-1000
100
0.4
±8
1.0
10
1.0
3.5
1.1
2
SG1526B/2526B
0.4.
150
Min. Typ. Max. Min. Typ. Max.
500
2.5
0.5
±3
0.5
7
3.0
1.0
1.0
500
2.5
0.5
±3
0.5
3
3.0
1.0
1.0
±8
1.0
5
1.0
3.5
1.1
2
%
%
%
Hz
KHz
V
V
µs
64
3.6
70
66
2
-350
35
72
4.2
0.2
94
80
60
3.6
70
66
2
-350
35
72
4.2
0.2
94
80
10
-2000
200
0.4
mV
nA
nA
dB
V
V
dB
dB
PWM Comparator Section (Note 4)
Digital Ports (SYNC, SHUTDOWN, and RESET)
HIGH Output Voltage
LOW Output Voltage
HIGH Input Current
LOW Input Current
SHUTDOWN Delay to Output
Current Limit Comparator Section
(Note 6)
Sense Voltage
Input Bias Current
Delay to Output
(Note 9)
120
-10
400
100
-3
80110
-10
400
100
-3
90
Output Drivers (each output)
(Note 7)
50
0.1
100 50
0.1
100
0.4.
150VµA
V
V
V
V
µA
µs
µs
0.3
2
150
0.4
0.15
13.5
13
0.2
1.2
50
0.3
0.1
12.5
12
13.5
13
0.2
1.2
50
0.3
0.1
12.5
12
Power Consumption Section (Note 8)
SHUTDOWN = 0.4V 18 30 18 30 mA
Page 4
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
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SG1526B/SG2526B/SG3526B
FIGURE 1.
REFERENCE VOLTAGE VS. SUPPLY VOLTAGE
FIGURE 3.
REFERENCE SHORT CIRCUIT
FIGURE 2.
REFERENCE TEMPERATURE STABILITY
FIGURE 6.
ERROR AMPLIFIER OPEN LOOP GAIN
VS. FREQUENCY
FIGURE 5.
UNDER VOLTAGE LOCKOUT
FIGURE 7.
SOFTSTART TIME CONSTANT VS. C
S
FIGURE 9.
COMPARATOR INPUT TO DRIVER OUTPUT DELAY
FIGURE 8.
CURRENT LIMIT TRANSFER FUNCTION
CHARACTERISTIC CURVES
FIGURE 4.
REFERENCE RIPPLE REJECTION
Page 5
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
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SG1526B/SG2526B/SG3526B
FIGURE 10.
STANDBY CURRENT VS. SUPPLY VOLTAGE
FIGURE 12.
OUTPUT DRIVER DEADTIME VS. RD VALUE
FIGURE 11.
OUTPUT DRIVER DEADTIME VS. CT VALUE
FIGURE 15.
SUPPLY CURRENT VS. OUTPUT FREQUENCY
FIGURE 14.
SUPPLY CURRENT VS. OUTPUT FREQUENCY
FIGURE 16.
OSCILLATOR FREQUENCY
TEMPERATURE STABILITY
FIGURE 18.
SHUTDOWN INPUT TO DRIVER OUTPUT DELAY
FIGURE 17.
OUTPUT DRIVER SATURATION VOLTAGE
CHARACTERISTIC CURVES (continued)
FIGURE 13.
SUPPLY CURRENT VS. OUTPUT FREQUENCY
Page 6
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
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SG1526B/SG2526B/SG3526B
FIGURE 19.
OSCILLATOR PERIOD VS. RT AND C
T
APPLICATION INFORMATION
CHARACTERISTIC CURVES (continued)
VOLTAGE REFERENCE
The reference regulator of the SG1526B is a “band-gap” type; that is, the precision +5 volt
output is derived from the very predictable base-emitter voltage of an NPN transistor.
Since this is a sub-surface phenomenon, the resulting output exhibits excellent stability
compared to earlier surface-breakdown zener designs.
The reference output is stabilized at input voltages as low as +8 volts, and can provide
up to 20mA of load current to external circuitry. An external PNP transistor can be used
to boost the available current to many hundreds of mA. A rugged low-frequency audiotype transistor should be used, and lead lengths between the PWM and transistor should
be as short as possible to minimize the risk of oscillation.
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit protects the SG1526B and the power devices it controls
from inadequate supply voltage. If +V
IN
is too low, the circuit disables the output drivers
and holds the RESET pin LOW. This prevents spurious output pulses while the control
circuitry is stabilizing, and holds the soft-start timing capacitor in a discharged state.
The circuit consists of a merged bandgap reference and comparator circuit which is
active when the reference voltage has risen to 2V
BE
or 1.2 volts at 25oC. When the
reference voltage rises to approximately +4.4 volts, the circuit enables the output drivers
and releases the RESET pin, allowing a normal softstart. The comparator has 200mV
of hysteresis to minimize oscillation at the trip point. When +V
IN
to the PWM is removed
and the reference drops to +4.2 volts, the undervoltage circuit pulls RESET LOW again.
The soft-start capacitor is immediately discharged, and the PWM is ready for another
soft-start cycle.
The SG1526B can operate from a +5 volt supply regulated to within ±4% by connecting
the V
REF
pin to the +VIN pin.
FIGURE 21.
SIMPLIFIED UNDERVOLTAGE LOCKOUT
The soft-start circuit protects the power transistors and rectifier diodes from high current
surges during power supply turn-on. When supply voltage is first applied to the
SG1526B, the undervoltage lockout circuit holds RESET LOW with Q3. Q1 is turned on,
which holds the soft-start capacitor voltage at zero. The second collector of Q1 clamps
the output of the error amplifier to ground, guaranteeing zero duty cycle at the driver
outputs. When the supply voltage reaches normal operating range, RESET will go HIGH.
Q1 turns off, allowing the internal 100µA current source to charge C
S
. Q2 clamps the error
amplifier output to 1.0 V
BE
above the voltage on CS. As the soft-start voltage ramps up
to +5 volts, the duty cycle of the PWM linearly increases to whatever value the voltage
regulation loop requires for an error null. Figure 7 gives the timing relationship between
C
S
ramp time to 100% duty cycle.
FIGURE 20.
EXTENDING REFERENCE OUTPUT CURRENT
FIGURE 22.
SOFT-START CIRCUIT SCHEMATIC
SOFT-START CIRCUIT
Page 7
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
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SG1526B/SG2526B/SG3526B
APPLICATION INFORMATION (continued)
DIGITAL CONTROL PORTS
The three digital control ports of the SG1526B are bidirectional. Each pin can drive TTL and 5 volt CMOS logic
directly, up to a fan-out of 10 low-power Schottky gates.
Each pin can also be directly driven by open-collector TTL,
open-drain CMOS, and open-collector voltage comparators,
fan-in is equivalent to 1 low-power Schottky gate. Each port
is normally HIGH; the pin is pulled LOW to activate the
particular function. Driving SYNC LOW initiates a discharge
cycle in the oscillator. Pulling SHUTDOWN LOW immediately inhibits all PWM output pulses. Holding RESET LOW
discharges the soft-start capacitor. The logic threshold is
+1.1 volts at +25oC. Noise immunity can be gained at the
expense of fan-out with an external 2K pull-up resistor to +5
volts.
OSCILLATOR
The oscillator is programmed for frequency and dead time
with three components: R
T CT
, and RD. Two waveforms are
generated: a sawtooth waveform at pin 10 for pulse width
modulation, and a logic clock at pin 12. The following
procedure is recommended for choosing timing values:
1. With R
D
= 0Ω (pin 11 shorted to ground) select values
for R
T
and CT from Figure 19 to give the desired
oscillator period. Remember that the frequency at
each driver output is half the oscillator frequency, and
the frequency at the +V
C
terminal is the same as the
oscillator frequency.
2. If more dead time is required, select a larger value of
R
D
using Figure 14 as a guide. At 40 KHz dead time
increases by 300 ns/Ω.
3. Increasing the dead time will cause the oscillator
frequency to decrease slightly. Go back and decrease the value of R
T
slightly to bring the frequency
back to the nominal design value.
The SG1526B can be synchronized to an external logic clock
by programming the oscillator to free-run at a frequency 10%
slower than the sync frequency. A periodic LOW logic pulse
approximately 0.5 µSec wide at the SYNC pin will then lock
the oscillator to the external frequency.
Multiple devices can be synchronized together by programming one master unit for the desired frequency, and then
sharing its sawtooth and clock waveforms with the slave
units. All C
T
terminals are connected to the CT pin of the
master, and all SYNC terminals are likewise connected to
the SYNC pin of the master. Slave R
T
terminals should not
be left open; at least 50K should be connected from each pin
to ground. Slave R
D
terminals may be either left open or
grounded.
FIGURE 24.
OSCILLATOR CONNECTIONS ANDD WAVEFORMS
ERROR AMPLIFIER
The error amplifier is a transconductance design, with an
output impedance of 2 megohms. Since all voltage gain
takes place at the output pin, the open-loop gain/frequency
characteristics can be controlled with shunt reactance to
ground. When compensated for unity-gain stability with 100
pF, the amplifier has an open-loop pole at 400 Hz.
The input connections to the error amplifier and determined
by the polarity of the switching supply output voltage. For
positive supplies, the common-mode voltage is +5.0 volts
and the feedback connections in Figure 25A are used. With
negative supplies, the common-mode voltage is ground and
the feedback divider is connected between the negative
output and the +5.0 volt reference voltage, as shown in
Figure 25B.
FIGURE 25.
ERROR AMPLIFIER CONNECTIONS
FIGURE 23
DIGITAL CONTROL PORT SCHEMATIC
(A) (B)
Page 8
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
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SG1526B/SG2526B/SG3526B
APPLICATION INFORMATION (continued)
OUTPUT DRIVERS
The totem-pole output drivers of the SG1526B are designed
to source and sink 100mA continuously and 200mA peak.
Loads can be driven either from the output pins 13 and 16,
or from the +V
C
pin, as required. Curves for the saturation
voltage at these outputs as a function of load current are
found in Figure 17.
FIGURE 26.
PUSH-PULL CONFIGURATION
FIGURE 28.
DRIVING N-CHANNEL POWER MOSFETS
FIGURE 27.
SINGLE-ENDED CONFIGURATION
SG1526B LAB TEST FIXTURE
Page 9
4/90 Rev 1.1 2/94 LINFINITY Microelectronics Inc.
Copyright 1994 11861 Western Avenue
∞ ∞
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SG1526B/SG2526B/SG3526B
CONNECTION DIAGRAMS & ORDERING INFORMATION (See Notes Below)
10
1
2
3
4
5
6
7
8
9
16
15
14
13
12
11
17
18
18-PIN CERAMIC DIP
J - PACKAGE
Ambient
Temperature Range
SG1526BJ/883B -55°C to 125°C
JAN1526BJ -55°C to 125°C
SG1526BJ/DESC -55°C to 125°C
SG1526BJ -55°C to 125°C
SG2526BJ -55°C to 125°C
SG3526BJ 0°C to 70°C
Part No.Package Connection Diagram
SHUTDOWN
COMPENSATION
- ERROR
+ ERROR
V
COLLECTOR
OUTPUT A
GROUND
C
T
R
DEADTIME
SYNC
V
REF
+V
IN
OUTPUT B
C
SOFTSTART
R
T
RESET
- CURRENT SENSE
+ CURRENT SENSE
Note1. Contact factory for JAN and DESC product availability.
2. All parts are viewed from the top.
1
16
15
14
13
12
11
10
17
18
2
3
4
5
6
7
8
9
COMPENSATION
-ERROR
+ERROR
C
SOFTSTART
RESET
- CURRENT SENSE
+ CURRENT SENSE
+V
COLLECTOR
OUTPUT A
GROUND
R
DEADTIME
SYNC
V
REF
+V
IN
OUTPUT B
C
T
SHUTDOWN
R
T
18-PIN WIDE BODY
PLASTIC S.O.I.C.
DW - PACKAGE
SG2526BDW -25°C to 85°C
SG3526BDW 0°C to 70°C
20-PIN CERAMIC
LEADLESS CHIP CARRIER
L- PACKAGE
4
5
6
7
8
321
911121310
14
15
16
17
18
20 19
SG1526BL/883B -55°C to 125°C
SG1526BL -55°C to 125°C
11. C
T
12. R
DEADTIME
13. SYNC
14. OUTPUT A
15. +V
COLLECTOR
16. N.C.
17. GROUND
18. OUTPUT B
19. +V
IN
20. V
REF
1. N.C.
2. +ERROR
3. -ERROR
4. COMP
5. C
SOFTSTART
6. RESET
7. - C.S.
8. + C.S.
9. SHUTDOWN
10. R
T
SG2526BN -25°C to 85°C
SG3526BN 0°C to 70°C
18-PIN PLASTIC DIP
N - PACKAGE
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