D E S C R I P T I O N
The SG1825C is a high-performance
pulse width modulator optimized for
high frequency current-mode power
supplies. Included in the controller
are a precision voltage reference,
micropower start-up circuitry, soft-
start, high-frequency oscillator,
wideband error amplifier, fast current-
limit comparator, full double-pulse
suppression logic, and dual totem-
pole output drivers. Innovative
circuit design and an advanced linear
Schottky process result in very short
propagation delays through the
K E Y F E AT U R E S
s
s
s
s
s
IMPROVED REFERENCE INITIAL
TOLERANCE (±1% max.)
s
s
s
s
s
IMPROVED OSCILLATOR INITIAL
ACCURACY (±3% typ.)
s
s
s
s
s
IMPROVED STARTUP CURRENT
(500µA typ.)
s
s
s
s
s
PROP DELAY TO OUTPUTS (50ns typ.)
p 10V TO 30V OPERATION
p 5.1V REFERENCE TRIMMED TO ±1%
p 2MHZ OSCILLATOR CAPABILITY
p 1.5A PEAK TOTEM-POLE DRIVERS
p U.V. LOCKOUT WITH HYSTERESIS
p NO OUTPUT DRIVER "FLOAT"
p PROGRAMMABLE SOFTSTART
p DOUBLE-PULSE SUPPRESSION LOGIC
p WIDEBAND LOW-IMPEDANCE ERROR
AMPLIFIER
p CURRENT-MODE OR VOLTAGE-MODE
CONTROL
p WIDE CHOICE OF HIGH-FREQUENCY
PACKAGES
HIGH RELIABILITY FEATURES
s
s
s
s
s
AVAILABLE TO MIL-STD-883B
s
s
s
s
s
LINFINITY LEVEL "S" PROCESSING AVAIL.
P R O D U C T H I G H L I G H T
I
N I T I A L
O
S C I L L A T O R
A
C C U R A C Y
P A C K A G E O R D E R I N F O R M A T I O N
T
J
(°C)
Plastic DIP
16-pin
0 to 70
SG3825CN
SG3825CDW
SG3825CQ
SG3825CJ
-25 to 85
SG2825CN
SG2825CDW
SG2825CQ
SG2825CJ
-55 to 125
SG1825CJ
SG1825CL
MIL-STD-883
SG1825CJ/883B
SG1825CL/883B
DESC
SG1825CJ/DESC
SG1825CL/DESC
N
Plastic Wide SOIC
16-pin
DW
Plastic LCC
20-pin
Q
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. SG3825CDWT)
Ceramic DIP
16-pin
J
L
Ceramic LCC
20-pin
H
I G H
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P E E D
C
U R R E N T
- M
O D E
P W M
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E C O M M E N D E D
F O R
N
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D
E S I G N S
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O V A T I O N
Copyright © 1994
Rev. 1.3 6/96
F O R F U R T H E R I N F O R M A T I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841
SG1825C/SG2825C/SG3825C
LIN D
O C
#: 1825
1
current limit comparator, logic, and
output drivers. This device can be
used to implement either current-
mode or voltage-mode switching
power supplies. It also is useful as
a series-resonant controller to
frequencies beyond 1MHz. The
SG1825C is specified for operation
over the full military ambient tem-
perature range of -55°C to 125°C.
The SG2825C is characterized for the
industrial range of -25°C to 85°C,
and the SG3825C is selected for the
commercial range of 0°C to 70°C.
0
5
15
10
390
395
400
405
410
Initial Oscillator Accuracy - KHz
Percentage of Units - %
415
Sample Size = 45
Mean 411.887
Std. Dev. = 4.3
Sample Size = 279
Mean 401.661
Std. Dev. = 3.8
H
I G H
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P E E D
C
U R R E N T
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O D E
P W M
SG1825C/SG2825C/SG3825C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright © 1994
Rev. 1.3 6/96
2
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (V
IN
and V
C
) .......................................................................................... 30V
Analog Inputs:
Error Amplifier and Ramp ........................................................................ -0.3V to 7.0V
Softstart and I
LIM
/S.D. ................................................................................ -0.3V to 6.0V
Digital Input (Clock) .................................................................................... 1.5V to 6.0V
Driver Outputs ........................................................................................ -0.3V to V
C
+1.5V
Source / Sink Output Current (each output):
Continuous .............................................................................................................. 0.5A
Pulse, 500ns ............................................................................................................ 2.0A
Softstart Sink Current................................................................................................ 20mA
Clock Output Current ................................................................................................. 5mA
Error Amplifier Output Current ................................................................................. 5mA
Oscillator Charging Current ....................................................................................... 5mA
Operating Junction Temperature:
Hermetic (J, L Package) ....................................................................................... 150°C
Plastic (DW, N, Q Packages) ............................................................................... 150°C
Storage Temperature Range...................................................................... -65°C to 150°C
Lead Temperature (soldering, 10 seconds) ............................................................ 300°C
PACKAGE PIN OUTS
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
J & N PACKAGE
(Top View)
4
5
6
7
8
3
2
1
9
11 12 13
10
14
15
16
17
18
20 19
DW PACKAGE
(Top View)
Note 1. Exceeding these ratings could cause damage to the device.
N PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θθθθθ
JA
65°C/W
DW PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θθθθθ
JA
95°C/W
Q PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θθθθθ
JA
80°C/W
J PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θθθθθ
JA
80°C/W
L PACKAGE:
THERMAL RESISTANCE-JUNCTION TO CASE,
θθθθθ
JC
35°C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θθθθθ
JA
120°C/W
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
THERMAL DATA
INV. INPUT
N.I. INPUT
E/A OUTPUT
CLOCK
R
T
C
T
RAMP
SOFTSTART
V
REF
+V
IN
OUTPUT B
V
C
PWR GND
OUTPUT A
GROUND
I
LIM
/ S.D.
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
+V
REF
+V
IN
OUTPUT B
V
C
PWR GND
OUTPUT A
GROUND
I
LIM
/ S.D.
INV. INPUT
N.I. INPUT
E/A OUTPUT
CLOCK
R
T
C
T
RAMP
SOFTSTART
11. N.C.
12. I
LIM
/ S.D.
13. GROUND
14. OUTPUT A
15. PWR GND
16. N.C.
17. V
C
18. OUTPUT B
19. +V
IN
20. V
REF
1. N.C.
2. INV. INPUT
3. N.I. INPUT
4. E/A OUTPUT
5. CLOCK
6. N.C.
7. R
T
8. C
T
9. RAMP
10. SOFTSTART
L PACKAGE
(Top View)
Q PACKAGE
(Top View)
3
2
1 20 19
4
18
17
5
6
16
15
7
8
14
9
11 12 13
10
H
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U R R E N T
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P W M
SG1825C/SG2825C/SG3825C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
3
Copyright © 1994
Rev. 1.3 6/96
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Supply Voltage Range
Voltage Amp Common Mode Range
Ramp Input Voltage Range
Current Limit / Shutdown Voltage Range
Source / Sink Output Current
Continuous
Pulse, 500ns
Voltage Reference Output Current
Oscillator Frequency Range
Oscillator Charging Current
Oscillator Timing Resistor
R
T
Oscillator Timing Capacitor
C
T
Operating Ambient Temperature Range:
SG1825C
T
A
SG2825C
T
A
SG3825C
T
A
R E C O M M E N D E D O P E R AT I N G C O N D I T I O N S
(Note 2)
Parameter
Symbol
Units
Recommended Operating Conditions
Min.
Typ.
Max.
10
30
V
1.5
5.5
V
0
5.0
V
0
4.0
V
200
mA
1.0
A
1
10
mA
4
1500
kHz
0.030
3
mA
1
100
k
Ω
0.470
10
nF
0
70
°C
-25
85
°C
-55
125
°C
Note 2. Range over which the device is functional.
E L E C T R I C A L C H A R A C T E R I S T I C S
(Note 3)
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG3825C with 0°C
≤
T
A
≤
70°C, SG2825C with
-25°C
≤
T
A
≤
85°C, SG1825C with -55°C
≤
T
A
≤
125°C, and V
IN
=V
C
=15V. Low duty cycle pulse testing techniques are used which maintains junction
and case temperatures equal to the ambient temperature.)
Reference Section
Parameter
Symbol
Test Conditions
Output Voltage
T
J
= 25°C, I
L
= 1mA
Line Regulation
V
IN
= 10 to 30V
Load Regulation
I
L
= 1 to 10mA
Temperature Stability (Note 3)
Over Operating Temperature
Total Output Range (Note 3)
Over Line, Load, and Temperature
Output Noise Voltage (Note 3)
f = 10Hz to 10kHz, I
L
= 0mA
Long Term Stability (Notes 3 &4)
T
J
= 125°C, t = 1000hrs
Short Circuit Current
V
REF
= 0V
Oscillator Section
(Note 5)
Initial Accuracy
T
J
= 25°C, C
CLK
≤
10pF
Voltage Stability
V
IN
= 10 to 30V
Temperature Stability (Note 3)
Over Rated Operating Temperature
Total Frequency Limits (Note 3)
Over Line and Temperature
Minimum Frequency
R
T
= 100K
Ω
, C
T
= 0.01µF
Maximum Frequency
R
T
= 1K
Ω
, C
T
= 470pF
Clock High Level
I
CLK
= -1mA
Clock Low Level
I
CLK
= -1mA
Ramp Peak Voltage
Ramp Valley Voltage
Valley-to-Peak Amplitude
Note 3. This parameter is guaranteed by design and process control, but is not 100% tested in production.
Note 4. This parameter is non-accumulative, and represents the random fluctuation of the reference voltage within some error band when observed
over any 1000 hour period of time.
SG3825C
Units
Min. Typ. Max. Min. Typ. Max.
SG1825C/2825C
5.05 5.10 5.15 5.05 5.10 5.15
V
2
15
2
15
mV
5
15
5
15
mV
0.2
0.4
0.2
0.4
mV/°C
5.00
5.20 5.00
5.20
V
50
200
50
µV
RMS
5
25
5
25
mV
-15
-50 -100 -15
-50 -100
mA
370 400 430 370 400 430
kHz
0.2
2
0.2
2
%
5
8
5
8
%
350
450 350
450
kHz
4
4
kHz
1.5
1.5
MHz
3.9
4.5
3.9
4.5
V
2.3
2.9
2.3
2.9
V
2.6
2.8
3.0
2.6
2.8
3.0
V
0.7
1.0 1.25 0.7
1.0 1.25
V
1.6
1.8
2.0
1.6
1.8
2.0
V
H
I G H
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P E E D
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U R R E N T
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P W M
SG1825C/SG2825C/SG3825C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright © 1994
Rev. 1.3 6/96
4
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E L E C T R I C A L C H A R A C T E R I S T I C S
(Cont'd.)
Parameter
Symbol
Test Conditions
Error Amplifier Section
(Note 6)
Input Offset Voltage
R
S
≤
2K
Ω
, V
ERROR
= 2.5V
Input Bias Current
V
ERROR
= 2.5V
Input Offset Current
V
ERROR
= 2.5V
DC Open Loop Gain
A
VOL
V
ERROR
= 1 to 4V
Common Mode Rejection
Over Rated Voltage Range, V
ERROR
= 2.5V
Power Supply Rejection
V
IN
= 10V to 30V, V
ERROR
= 2.5V
Output Sink Current
V
ERROR
= 1V
Output Source Current
V
ERROR
= 4V
Output High Voltage
I
ERROR
= -0.5mA
Output Low Voltage
I
ERROR
= 1mA
Unity Gain Bandwidth (Note 3)
A
VOL
= 0dB
Slew Rate (Note 3)
PWM Comparator Section
(Note 5 & 7)
Ramp Input Bias Current
Minimum Duty Cycle
V
ERROR
= 1V
Maximum Duty Cycle (Note 8)
V
ERROR
= 4V
Zero Duty Cycle Threshold
Delay to Driver Output (Note 3)
V
RAMP
= 0V to 2V, V
ERROR
= 2V
Softstart Section
C
SS
Charge Current
V
SOFTSTART
= 0.5V
C
SS
Discharge Current
V
SOFTSTART
= 1.0V
Current Limit / Shutdown Section
(Note 9)
I
LIM
Input Bias Current
Current Limit Threshold
Shutdown Threshold
Delay to Driver Output (Note 3)
V
SHUTDOWN
= 0V to 1.2V
Output Drivers Section (each output)
Output Low Level
I
SINK
= 20mA
I
SINK
= 200mA
Output High Level
I
SOURCE
= 20mA
I
SOURCE
= 200mA
V
C
Standby Current
V
C
= 30V
Output Rise / Fall Time (Note 3)
C
L
= 1000pF
Undervoltage Lockout Section
Start Threshold Voltage
UV Lockout Hysteresis
Supply Current Section
(Note 5)
Start Up Current
V
IN
= 8V
Operating Current
V
INV
, V
RAMP
, V(I
LIM
/S.D.) = 0V, V
N.I.
= 1V
Note 5. F
OSC
= 400kHz (R
T
= 3.65k
Ω
, C
T
= 1.0nF).
Note 6. V
CM
= 1.5V to 5.5V.
Note 7. V
RAMP
= 0V, unless otherwise specified.
Note 8. 100% duty cycle is defined as a pulsewidth equal to one oscillator period.
Note 9. V(I
LIM
/S.D.) = 0V to 4.0V, unless otherwise specified.
SG3825C
Units
Min. Typ. Max. Min. Typ. Max.
SG1825C/2825C
15
15
mV
0.6
3
0.6
3
µA
0.1
1
0.1
1
µA
60
95
60
95
dB
75
95
75
95
dB
85
110
85
110
dB
1
2.5
1
2.5
mA
-0.5 -1.3
-0.5 -1.3
mA
4.0
4.7
5.0
4.0
4.7
5.0
V
0
0.5
1.0
0
0.5
1.0
V
3
5.5
3
5.5
MHz
6
6
V/µsec
-1
-5
-1
-5
µA
0
0
%
85
85
%
1.1 1.25
1.1 1.25
V
50
80
50
80
ns
3
9
20
3
9
20
µA
1
1
mA
±15
±10
µA
0.9
1.0
1.1
0.9
1.0
1.1
V
1.25 1.40 1.55 1.20 1.40 1.55
V
50
80
50
80
ns
0.25 0.40
0.25 0.40
V
1.2
2.0
1.2
2.0
V
13.0 13.5
13.0 13.5
V
12.0 13.0
12.0 13.0
V
150 500
150 500
µA
30
60
30
60
ns
8.8
9.2
9.7
8.8
9.2
9.7
V
0.4
0.8
1.2
0.4
0.8
1.2
V
0.5
1.2
0.5
1.2
mA
22
33
22
33
mA
H
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P W M
SG1825C/SG2825C/SG3825C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
5
Copyright © 1994
Rev. 1.3 6/96
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B L O C K D I A G R A M
FIGURE INDEX
Application Circuits
FIGURE #
1.
HIGH-SPEED LAYOUT AND BYPASSING
2.
MICROPOWER STARTUP
3.
SOFTSTART FAST RESET
4.
OSCILLATOR SYCHRONIZATION
5.
OSCILLATOR FUNCTIONAL DIAGRAM
6.
VOLTAGE AMPLIFIER CONNECTIONS
7.
DRIVING SHIELDED CABLE
+9V
REFERENCE
REGULATOR
15
10
16
OSCILLATOR
5
6
4
+ 4.0V
S
R Q
7
1.25V
3
ERROR
2
1
8
+ 1.4V
9
11
I
LIM
/S.D.
OUTPUT A
V
REF
+V
IN
GND
CLOCK
R
T
C
T
RAMP
E/A OUTPUT
N.I. INPUT
INV. INPUT
SOFTSTART
9µA
+ 1.0V
12 POWER GND
14 OUTPUT B
Q
Q
T
13 V
C
H
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P E E D
C
U R R E N T
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P W M
SG1825C/SG2825C/SG3825C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright © 1994
Rev. 1.3 6/96
6
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APPLICATION INFORMATION
The SG1825C, like all high-speed circuits, requires extra attention to external
conductor and component layout to minimize undesired inductive and
capacitive effects. All lead lengths must be as short as possible. The best
printed circuit board choice would be a four-layer design, with the two
internal planes supplying power and ground. Signal interconnects should
be placed on the outside, giving a conductor-over-ground-plane
(microstrip) configuration. A two-sided printed circuit board with one side
dedicated as a ground plane is next best, and requires careful component
placement by a skilled pc designer.
Two supply bypass capacitors should be employed: a low-inductance
0.1µF ceramic within 0.25 inches of the +V
IN
pin for high frequencies, and
a 1 to 5µF solid tantalum within 0.5 inches of the V
C
pin to provide an energy
reservoir for the high-peak output currents. A low-inductance .01µF bypass
for the reference outpu