SG1525A/SG2525A/SG3525A
SG1527A/SG2527A/SG3527A
REGULATING PULSE WIDTH MODULATOR
DESCRIPTION
The SG1525A/1527A series of pulse width modulator integrated circuits are
designed to offer improved performance and lower external parts count when used
to implement all types of switching power supplies. The on-chip +5.1 volt reference
is trimmed to ±1% initial accuracy and the input common-mode range of the error
amplifier includes the reference voltage, eliminating external potentiometers and
divider resistors. A Sync input to the oscillator allows multiple units to be slaved
together, or a single unit to be synchronized to an external system clock. A single
resistor between the C
T
pin and the Discharge pin provides a wide range of deadtime
adjustment. These devices also feature built-in soft-start circuitry with only a timing
capacitor required externally. A Shutdown pin controls both the soft-start circuitry
and the output stages, providing instantaneous turn-off with soft-start recycle for
slow turn-on. These functions are also controlled by an undervoltage lockout which
keeps the outputs off and the soft-start capacitor discharged for input voltages less
than that required for normal operation. Another unique feature of these PWM
circuits is a latch following the comparator. Once a PWM pulse has been terminated
for any reason, the outputs will remain off for the duration of the period. The latch
is reset with each clock pulse. The output stages are totem-pole designs capable
of sourcing or sinking in excess of 200mA. The SG1525A output stage features
NOR logic, giving a LOW output for an OFF state. The SG1527A utilizes OR logic
which results in a HIGH output level when OFF.
FEATURES
•
•
•
•
•
•
•
•
8V to 35V operation
5.1V reference trimmed to ±1%
100Hz to 500KHz oscillator range
Separate oscillator sync terminal
Adjustable deadtime control
Internal soft-start
Input undervoltage lockout
Latching P.W.M. to prevent multiple
pulses
•
Dual source/sink output drivers
HIGH RELIABILITY FEATURES
- SG1525A, SG1527A
♦
Available to MIL-STD-883B
♦
MIL-M38510/12602BEA - JAN1525AJ
♦
MIL-M38510/12604BEA - JAN1527AJ
♦
Radiation data available
♦
LMI level "S" processing available
BLOCK DIAGRAM
Rev 1.4a
3/19/2005
Copyright
©
1996
1
11861 Western Avenue
∞
Garden Grove, CA 92841
(714) 898-8121
∞
FAX: (714) 893-2570
Microsemi Inc.
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (+V
IN
) ....................................................... 40V
Collector Supply Voltage (V
C
) ........................................... 40V
Logic Inputs ....................................................... -0.3V to 5.5V
Analog Inputs ....................................................... -0.3V to V
IN
Output Current, Source or Sink ................................... 500mA
Reference Load Current ............................................... 50mA
Note 1. Values beyond which damage may occur.
Oscillator Charging Current ............................................
Operating Junction Temperature Range
Hermetic (J, L Packages) .....................................
Plastic (N, DW Packages ) .......................................
Storage Temperature Range .......................... -65°C to
Lead Temperature (Soldering, 10 seconds) .................
5mA
150°C
150°C
150°C
300°C
RoHS Peak Package Solder Reflow Temp. (40 sec. max. exp.)...... 260°C(+0, -5)
THERMAL DATA
J Package:
Thermal Resistance-
Junction to Case
,
θ
JC
.................. 30°C/W
Thermal Resistance-
Junction to Ambient
,
θ
JA
.............. 80°C/W
DW Package:
Thermal Resistance-
Junction to Case
,
θ
JC
.................. 40°C/W
Thermal Resistance-
Junction to Ambient
,
θ
JA
............. 95°C/W
L Package:
Thermal Resistance-
Junction to Case
,
θ
JC
.................. 35°C/W
Thermal Resistance-
Junction to Ambient
,
θ
JA
........... 120°C/W
N Package:
Thermal Resistance-
Junction to Case
,
θ
JC
................... 40°C/W
Thermal Resistance-
Junction to Ambient
,
θ
JA
............. 65°C/W
Note A. Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
Note B. The above numbers for
θ
JC
are maximums for the limiting
thermal resistance of the package in a standard mount-
ing configuration. The
θ
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.
RECOMMENDED OPERATING CONDITIONS
(Note 2)
Input Voltage (+V
IN
) ................................................ 8V to 35V
Collector Voltage (V
C
) .......................................... 4.5V to 35V
Sink/Source Load Current (steady state) ............. 0 to 100mA
Sink/Source Load Current (peak) ......................... 0 to 400mA
Reference Load Current ........................................ 0 to 20mA
Oscillator Frequency Range ....................... 100Hz to 350KHz
Oscillator Timing Resistor (R
T
) ........................ 2KΩ to 150KΩ
Note 2: Range over which the device is functional.
Deadtime Resistor Range (R
D
) ............................. 0Ω to 500Ω
Maximum Shutdown Source Impedance ......................... 5KΩ
Oscillator Timing Capacitor (C
T
) ................... 0.001µF to 0.1µF
Operating Ambient Temperature Range
SG1525A/SG1527A .................................... -55°C to 125°C
SG2525A/SG2527A ...................................... -25°C to 85°C
SG3525A/SG3527A ......................................... 0°C to 70°C
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG1525A/SG1527A with -55°C
≤
T
A
≤
125°C,
SG2525A/SG2527A with -25°C
≤
T
A
≤
85°C, SG3525A/SG3527A with 0°C
≤
T
A
≤
70°C, and +V
IN
= 20V. Low duty cycle pulse testing techniques are
used which maintains junction and case temperatures equal to the ambient temperature.)
ELECTRICAL CHARACTERISTICS
Parameter
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
(Note 3)
Total Output Voltage Range
(Note 3)
Short Circuit Current
Output Noise Voltage
(Note 3)
Long Term Stability
(Note 3)
Test Conditions
SG1525A/2525A
SG3525A
Units
SG1527A/2527A
SG3527A
Min. Typ. Max. Min. Typ. Max.
5.05 5.10
10
20
20
5.00
80
40
20
V
5.15 5.00 5.10 5.20
mV
30
10
30
mV
50
20
50
mV
50
20
50
V
5.25
5.20 4.95
mA
80 100
100
40 200
µVrms
200
50 mV/khr
20
50
T
J
= 25°C
V
IN
= 8V to 35V
I
L
= 0 to 20mA
Over Operating Temperature Range
Over Line, Load and Temperature
V
REF
= 0V, T
J
= 25°C
10Hz
≤
f
≤
10KHz, T
J
= 25°C
T
J
= 125°C
Note 3. These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production.
Note 4. F
OSC
= 40KHz (R
T
= 3.6KΩ, C
T
= 0.01µF, R
D
= 0Ω)
Note 5. Applies to SG1525A/2525A/3525A only, due to polarity of output pulses.
Rev 1.4a
Copyright
©
1996
2
11861 Western Avenue
∞
Garden Grove, CA 92841
(714) 898-8121
∞
FAX: (714) 893-2570
OUTPUT SECTION
FIGURE 6 -OUTPUT CIRCUIT (½ Circuit Shown)
FIGURE 7 - OUTPUT SATURATION CHARACTERISTICS
APPLICATION INFORMATION
For single-ended supplies, the driver outputs are grounded. The
V
C
terminal is switched to ground by the totem-pole source
transistors on alternate oscillator cycles.
In conventional push-pull bipolar designs, forward base drive is
controlled by R
1
- R
3
. Rapid turn-off times for the power devices
are achieved with speed-up capacitors C
1
and C
2
.
The low source impedance of the output drivers provides rapid
charging of power FET input capacitance while minimizing exter-
nal components.
Rev 1.4a
Low power transformers can be driven directly by the SG1525A.
Automatic reset occurs during deadtime, when both ends of the
primary winding are switched to ground.
Copyright
©
1996
5
11861 Western Avenue
∞
Garden Grove, CA 92841
(714) 898-8121
∞
FAX: (714) 893-2570
Analog electronics
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