4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
1
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
REGULATING PULSE WIDTH MODULATOR
FEATURES
8 to 35 volt operation
5V reference trimmed to 1%
1Hz to 350KHz oscillator range
Dual 100mA source/sink outputs
Digital current limiting
Double pulse suppression
Programmable deadtime
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
HIGH RELIABILITY FEATURES - SG1526
Available to MIL-STD-883B and DESC SMD
Radiation data available
LMI level "S"processing available
DESCRIPTION
The SG1526 is a high performance monolithic pulse width modulator
circuit designed for fixed-frequency switching regulators and other
power control applications. Included in an 18-pin dual-in-line package
are a temperature compensated voltage reference, sawtooth oscillator,
error amplifier, pulse width modulator, pulse metering and steering logic,
and two low impedance power drivers. Also included are protective
features such as soft-start and undervoltage lockout, digital current
limiting, double pulse inhibit, a data latch for single pulse metering,
adjustable deadtime, and provision for symmetry correction inputs. For
ease of interface, all digital control ports are TTL and B-series CMOS
compatible. Active LOW logic design allows wired-OR connections for
maximum flexibility. This versatile device can be used to implement
single-ended or push-pull switching regulators of either polarity, both
transformerless and transformer coupled. The SG1526 is characterized
for operation over the full military ambient junction temperature range of
-55C to +150C. The SG2526 is characterized for operation from -25C
to +150C, and the SG3526 is characterized for operation from 0C to
+125C.
+V
IN
To Internal
Circuitry
V
REF
METERING
F/F
TOGGLE
F/F
MEMORY
F/F
SYNC
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
S
D
S
T
Q
Q
Q
R
OUTPUT B
+V
C
OUTPUT A
BLOCK DIAGRAM
+V
IN
Amp
Q
Q
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
2
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
ABSOLUTE MAXIMUM RATINGS
(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
,
JC
.................. 25C/W
Thermal Resistance-
Junction to Ambient
,
JA
.............. 70C/W
N Package:
Thermal Resistance-
Junction to Case
,
JC
.................. 30C/W
Thermal Resistance-
Junction to Ambient
,
JA
............. 60C/W
DW Package:
Thermal Resistance-
Junction to Case
,
JC
.................. 35C/W
Thermal Resistance-
Junction to Ambient
,
JA
............. 90C/W
L Package:
Thermal Resistance-
Junction to Case
,
JC
................... 35C/W
Thermal Resistance-
Junction to Ambient
,
JA
........... 120C/W
Note A. Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
JA
).
Note B. The above numbers for
JC
are maximums for the limiting
thermal resistance of the package in a standard mount-
ing configuration. The
JA
numbers are meant to be
guidelines for the thermal performance of the device/pc-
board system. All of the above assume no ambient
airflow.
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 350KHz
2K
to 150K
Oscillator Timing Capacitor ....................................
Available Deadtime Range at 40KHz ......................
Operating Ambient Temperature Range:
SG1526 .........................................................
SG2526 ...........................................................
SG3526 ...............................................................
1nF to 20
F
3% 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.
RECOMMENDED OPERATING CONDITIONS
(Note 2)
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG1526 with -55
C
T
A
125
C, SG2526 with
-25
C
T
A
85
C, SG3526 with 0
C
T
A
70
C, and V
IN
= 15V. Low duty cycle pulse testing techniques are used which maintains junction and case
temperatures equal to the ambient temperature.)
Reference Section
(Note 3)
T
J
= 25
C
V
IN
= 8 to 35V
I
L
= 0 to 20mA
Over Operating T
J
Over Recommended Operating Conditions
V
REF
= 0V
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
(Note 9)
Total Output Voltage Range
(Note 9)
Short Circuit Current
SG3526
Units
Undervoltage Lockout Section
V
REF
= 3.8V
V
REF
= 4.8V
V
V
Parameter
Test Conditions
4.95
4.90
5.00
10
10
15
5.00
50
SG1526/2526
Min. Typ. Max.
2.4
0.2
4.8
0.4
5.05
30
30
50
5.10
125
4.90
4.85
5.00
10
10
15
5.00
50
5.10
30
50
50
5.15
125
V
mV
mV
mV
V
mA
Min. Typ. Max.
0.4
0.2
4.8
2.4
RESET Output Voltage
RESET Output Voltage
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
3
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
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
12.5
12
13.5
13
0.2
1.2
50
0.3
0.1
RESET = 0.4V
RESET = 2.4V
Error Clamp Voltage
C
S
Charging Current
50
0.1
100
Minimum Duty Cycle
Maximum Duty Cycle
V
COMPENSATION
= 0.4V
V
COMPENSATION
= 3.6V
45
49
0
R
S
2K
R
L
10M
,
T
J
= 25
C
V
PIN1
- V
PIN2
150mV, I
SOURCE
= 100
A
V
PIN2
- V
PIN1
150mV, I
SINK
= 100
A
R
S
2K
V
IN
= 8V to 35V
mV
nA
nA
dB
V
V
dB
dB
10
-2000
200
0.4
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
Current Limit Comparator Section
(Note 6)
R
S
50
,
T
J
= 25
C
mV
A
90
100
-3
110
-10
I
SOURCE
= 40
A
I
SINK
= 3.6mA
V
IH
= 2.4V
V
IL
= 0.4V
V
V
A
A
2.4
4
0.2
-125
-225
0.4
-300
-500
Oscillator Section
(Note 4)
T
J
= 25
C
V
IN
= 8 to 35V
Over Operating T
J
R
T
= 150K
, C
T
= 20
F
R
T
= 2K
, C
T
= 1.0nF
V
IN
= 35V
V
IN
= 8V
Initial Accuracy
Voltage Stability
Temperature Stability
(Note 9)
Minimum Frequency
(Note 9)
Maximum Frequency
Sawtooth Peak Voltage
Sawtooth Valley Voltage
SG3526
Test Conditions
Parameter
Units
ELECTRICAL CHARACTERISTICS
(continued)
350
0.5
3
0.5
7
3.0
1.0
SG1526/2526
Error Amplifier Section
(Note 5)
Min. Typ. Max. Min. Typ. Max.
8
1.0
10
1.0
3.5
350
0.5
3
0.5
5
3.0
1.0
8
1.0
10
1.0
3.5
%
%
%
Hz
KHz
V
V
64
3.6
70
66
2
-350
35
72
4.2
0.2
94
80
5
-1000
100
0.4
60
3.6
70
66
2
-350
35
72
4.2
0.2
94
80
PWM Comparator Section
(Note 4)
45
49
0
%
%
Digital Ports (SYNC, SHUTDOWN, and RESET)
HIGH Output Voltage
LOW Output Voltage
HIGH Input Current
LOW Input Current
2.4
4
0.2
-125
-225
0.4
-300
-500
Sense Voltage
Input Bias Current
80
100
-3
120
-10
Soft-Start Section
0.4
200
50
0.1
100
0.4
200
V
A
Output Drivers (each output)
(Note 7)
0.3
2
150
0.6
0.2
12.5
12
13.5
13
0.2
1.2
50
0.3
0.1
0.3
2
150
0.6
0.2
V
V
V
V
A
s
s
Power Consumption Section
(Note 8)
SHUTDOWN = 0.4V
Standby Current
18
30
18
30
mA
Note 3. I
L
= 0mA
Note 4. F
OSC
= 40KHz (R
T
= 4.12K
1%, C
T
= .01
F
1%, R
D
= 0
)
Note 5. V
CM
= 0 to 5.2V
Note 6. V
CM
= 0 to 12V
Note 7. V
C
= 15V
Note 8. V
IN
= 35V
Note 9. These parameters, although guaranteed over the recom-
mended operating conditions, are not tested in production.
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
4
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
FIGURE 1.
REFERENCE VOLTAGE VS. SUPPLY VOLTAGE
FIGURE 3.
REFERENCE SHORT CIRCUIT CURRENT
FIGURE 2.
REFERENCE TEMPERATURE STABILITY
FIGURE 6.
OUTPUT DRIVER DEADTIME VS. R
D
VALUE
FIGURE 5.
OSCILLATOR FREQUENCY TEMPERATURE
STABILITY
CHARACTERISTIC CURVES
FIGURE 4.
REFERENCE RIPPLE REJECTION
FIGURE 7.
OSCILLATOR PERIOD VS. R
T
AND C
T
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
5
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
FIGURE 8.
UNDERVOLTAGE LOCKOUT CHARACTERISTIC
FIGURE 10.
SOFTSTART TIME CONSTANT VS. C
S
FIGURE 9.
ERROR AMPLIFIER OPEN LOOP GAIN
VS. FREQUENCY
FIGURE 13.
SHUTDOWN INPUT TO DRIVER OUTPUT DELAY
FIGURE 12.
COMPARATOR INPUT TO DRIVER OUTPUT DELAY
FIGURE 14.
OUTPUT DRIVER SATURATION VOLTAGE VS. I
SINK
FIGURE 16.
STANDBY CURRENT VS. SUPPLY VOLTAGE
FIGURE 15.
OUTPUT SUPPLY SATURATION VOLTAGE VS. I
SINK
CHARACTERISTIC CURVES
(continued)
FIGURE 11.
CURRENT LIMIT TRANSFER FUNCTION
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
6
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
APPLICATION INFORMATION
VOLTAGE REFERENCE
The reference regulator of the SG1526 is based on a temperature compensated
zener diode. The circuitry is fully active at supply voltages above +8 volts., and
provides up to 20mA of load current to external circuitry at +5.0 volts. In systems
where additional current is required, an external PNP transistor can be used to
boost the available current. A rugged low frequency audio-type transistor should
be used, and lead lengths between the PWM and transistor should be as short as
possible to minimize the risk of oscillations. Even so, some types of transistors
may require collector-base capacitance for stability. Up to 1amp of load current
can be obtained with excellent regulation if the device selected maintains high
current gain.
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit protects the SG1526 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 +1.2 volt bandgap reference and comparator circuit which
is active when the reference voltage has risen to 3V
BE'
or 1.8 volts at 25C. When
the reference voltage rises to approximately +4.4 volts, the circuit enables the
output drivers and releases the RESET pin, allowing a normal soft-start. 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 undervolt-
age circuit pulls RESET LOW again. The soft-start capacitor is immediately
discharged, and the PWM is ready for another soft-start cycle.
The SG1526 can operate from a +5 volt supply by connecting the V
REF
pin to the
+V
IN
pin and maintaining the supply between +4.8 and +5.2 volts.
FIGURE 18.
SIMPLIFIED UNDERVOLTAGE LOCKOUT
SOFT-START CIRCUIT
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 SG1526, 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 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 100A current
source to charge C
S
. Q2 clamps the error amplifier output to 1V
BE
above the
voltage on C
S
. 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 10 gives the timing relationship between C
S
and ramp time
to 100% duty cycle.
FIGURE 19.
SOFT-START CIRCUIT SCHEMATIC
FIGURE 20.
DIGITAL CONTROL PORT SCHEMATIC
DIGITAL CONTROL PORTS
The three digital control ports of the SG1526 are bi-directional. 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 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 25C. Noise immunity can be gained at the
expense of fan-out with an external 2K pullup resistor to +5 volts.
FIGURE 17.
EXTENDING REFERENCE OUTPUT CURRENT
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
7
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
APPLICATION INFORMATION
(continued)
The oscillator is programmed for frequency and deadtime with three components: R
T
, C
T
, and R
D
. 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
= 0
(pin 11 shorted to ground) select values for R
T
and C
T
from Figure 7 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 6 as a guide. At 40kHz dead time increases by
400nSec/ohm.
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 SG1526 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 0.5Sec 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 C
T
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 nor should they
be tied to the +5V reference; at least 50K should be connected to each pin. Slave R
D
terminals may be either left open or
grounded.
OSCILLATOR
FIGURE 21 - OSCILLATOR CONNECTIONS AND WAVEFORMS
The error amplifier is a transconductance design, with an output impedance of 2 megohms and an effective output capacitance
of 100 pF. Since all voltage gain takes place at the output pin, the open-loop gain can be shaped with shunt reactance to ground.
For unity gain stability the amplifier requires an additional external 100 pF to ground, resulting in an open-loop pole at 400 Hz.
The input connections to the error amplifier are 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 22A 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 22B.
ERROR AMPLIFIER CONNECTIONS
FIGURE 22A
FIGURE 22B
ERROR AMPLIFIER
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
8
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
APPLICATION INFORMATION
(continued)
OUTPUT DRIVERS
The totem-pole output drivers of the SG1526 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 Figures 14 and 15.
Since the bottom transistor of the totem-pole is allowed to saturate, there is a momentary conduction path from the +V
C
terminal
to ground during switching. To limit the resulting current spikes a small resistor in series with pin 14 is always recommended.
The resistor value is determined by the driver supply voltage, and should be chosen for 200mA peak currents, as shown in
Figure 25.
SG1526 LAB TEST FIXTURE
FIGURE 23.
PUSH-PULL CONFIGURATION
FIGURE 25.
DRIVING N-CHANNEL POWER MOSFETS
FIGURE 24.
SINGLE-ENDED CONFIGURATION
4/90 Rev 1.1 2/94
L
INFINITY
Microelectronics Inc.
Copyright
1994
11861 Western Avenue
Garden Grove, CA 92841
9
(714) 898-8121
FAX: (714) 893-2570
SG1526/SG2526/SG3526
CONNECTION DIAGRAMS & ORDERING INFORMATION
(See Notes Below)
Ambient
Temperature Range
Part No.
Package
Connection Diagram
Note 1. Contact factory for JAN and DESC product availability.
2. All parts are viewed from the top.
10
1
2
3
4
5
6
7
8
9
16
15
14
13
12
11
17
18
18-PIN CERAMIC DIP
J - PACKAGE
SG1526J/883B
-55
C to 125
C
SG1526J
-55
C to 125
C
SG2526J
-25
C to 85
C
SG3526J
0
C to 70
C
SG2526N
-25
C to 85
C
SG3526N
0
C to 70
C
18-PIN PLASTIC DIP
N - PACKAGE
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
+V
COLLECTOR
OUTPUT A
GROUND
R
DEADTIME
SYNC
V
REF
+V
IN
OUTPUT B
C
T
1
18-PIN WIDE BODY
PLASTIC S.O.I.C.
DW - PACKAGE
SG2526DW
-25
C to 85
C
SG3526DW
0
C to 70
C
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
SHUTDOWN
R
T
20-PIN CERAMIC
LEADLESS CHIP CARRIER
L- PACKAGE
SG1526L/883B
-55
C to 125
C
SG1526L
-55
C to 125
C
4
5
6
7
8
3
2
1
9
11 12 13
10
14
15
16
17
18
20 19
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
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