L I N D
O C
# :
1844
SG1844/SG1845 Series
C
URRENT
M
ODE
PWM C
ONTROLLER
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O VA T I O N
P
R O D U C T I O N
D
A T A
S
H E E T
DESCRIPTION
The SG1844/45 family of control ICs
provides all the necessary features to
implement off-line fixed frequency,
current-mode switching power supplies
with a minimum number of external
components. Current-mode architecture
demonstrates improved line regulation,
improved load regulation, pulse-by-
pulse current limiting and inherent
protection of the power supply output
switch.
The bandgap reference is trimmed to
±1% over temperature. Oscillator
discharge current is trimmed to less than
±10%. The SG1844/45 has under-
voltage lockout, current-limiting circuitry
and start-up current of less than 1mA.
The totem-pole output is optimized to
drive the gate of a power MOSFET. The
output is low in the off state to provide
direct interface to an N-channel device.
Both operate up to a maximum duty
cycle range of zero to <50% due to an
internal toggle flip-flop which blanks the
output off every other clock cycle.
The SG1844/45 is specified for
operation over the full military ambient
temperature range of -55°C to 125°C.
The SG2844/45 is specified for the
industrial range of -25°C to 85°C, and
the SG3844/45 is designed for the
commercial range of 0°C to 70°C.
K E Y F E AT U R E S
s
OPTIMIZED FOR OFF-LINE CONTROL
s
LOW START-UP CURRENT (<1mA)
s
AUTOMATIC FEED FORWARD
COMPENSATION
s
TRIMMED OSCILLATOR DISCHARGE
CURRENT
s
PULSE-BY-PULSE CURRENT LIMITING
s
ENHANCED LOAD RESPONSE
CHARACTERISTICS
s
UNDER-VOLTAGE LOCKOUT WITH 6V
HYSTERESIS (SG1844 only)
s
DOUBLE PULSE SUPPRESSION
s
HIGH-CURRENT TOTEM-POLE OUTPUT
s
INTERNALLY TRIMMED BANDGAP
REFERENCE
s
500kHz OPERATION
s
UNDERVOLTAGE LOCKOUT
SG1844 - 16 volts
SG1845 - 8.4 volts
s
LOW SHOOT-THROUGH CURRENT <75mA
OVER TEMPERATURE
PRODUCT HIGHLIGHT
T
Y P I C A L
A
P P L I C AT I O N
OF
S G 3 8 4 4 I
N
A F
LY B A C K
C
O N V E R T E R
R
ST
HIGH RELIABILITY FEATURES
s
AVAILABLE TO MIL-STD-883B
s
LINFINITY LEVEL "S" PROCESSING AVAILABLE
AC
INPUT
I
ST
V
CC
SG3844
T
A
(°C)
0 to 70
-25 to 85
-55 to 125
MIL-STD/883
DESC
M
8-pin
Plastic DIP
N
PA C K A G E O R D E R I N F O R M AT I O N
Plastic DIP
Plastic SOIC
Plastic SOIC
Ceramic DIP
Ceramic DIP
DM
8-pin
D
14-pin
Y
8-pin
J
14-pin
14-pin
SG3844N
SG3845N
SG2844N
SG2845N
—
—
—
—
—
SG3844DM
SG3845DM
SG2844DM
SG2845DM
—
—
—
—
—
SG3844D
SG3845D
SG2844D
SG2845D
—
—
—
—
—
SG3844Y
SG3845Y
SG2844Y
SG2845Y
SG1844Y
SG1845Y
SG3844J
SG3845J
SG2844J
SG2845J
SG1844J
SG1845J
F
10-pin
—
—
—
—
—
—
—
—
Cer. Flatpack
L
20-pin
—
—
—
—
Ceramic LCC
SG3844M
SG3845M
SG2844M
SG2845M
—
—
—
—
—
SG1844L
SG1845L
SG1844L/883B
SG1845L/883B
SG1844Y/883B SG1844J/883B
SG1845Y/883B SG1845J/883B
SG1844Y/DESC SG1844J/DESC
SG1844F/DESC SG1844L/DESC
SG1845F/DESC SG1845L/DESC
—
—
SG1845Y/DESC SG1845J/DESC
Note: All surface-mount packages are available in Tape & Reel.
F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1
Copyright © 2000
Rev. 1.4 4/00
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841
1
PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
C
URRENT
-M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
A B S O L U T E M A X I M U M R AT I N G S
(Notes 1 & 2)
PACKAGE PIN OUTS
COM
V
FB
I
SENSE
R
T
/C
T
1
2
3
4
8
7
6
5
Supply Voltage (I
CC
< 30mA) ............................................................... Self Limiting
Supply Voltage (Low Impedance Source) ........................................................ 30V
Output Current (Peak) ....................................................................................... ±1A
Output Current (Continuous) ....................................................................... 350mA
Output Energy (Capacitive Load) ....................................................................... 5µJ
Analog Inputs (Pins 2, 3) ................................................................. -0.3V to +6.3V
Error Amp Output Sink Current ..................................................................... 10mA
Operating Junction Temperature
Hermetic (J, Y, F, L Packages) ................................................................... 150°C
Plastic (N, M, D, DM Packages) ................................................................ 150°C
Storage Temperature Range .......................................................... -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) .................................................. 300°C
Note 1. Exceeding these ratings could cause damage to the device.
Note 2. All voltages are with respect to Pin 5. All currents are positive into the specified
terminal.
V
REF
V
CC
OUT UT
GND
M & Y PACKAGE
(Top View)
COM
V
FB
I
SENSE
R
T
/C
T
1
2
3
4
8
7
6
5
V
REF
V
CC
OUT UT
GND
DM PACKAGE
(Top View)
COM
N.C.
V
FB
N.C.
I
SENSE
N.C.
R
T
/C
T
1
2
3
4
5
6
7
14
13
12
11
10
9
8
T H E R M A L D ATA
M PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
N PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
DM PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
D PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
Y PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
J PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
F PACKAGE:
THERMAL RESISTANCE-JUNCTION TO CASE,
θ
JC
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
L PACKAGE:
THERMAL RESISTANCE-JUNCTION TO CASE,
θ
JC
THERMAL RESISTANCE-JUNCTION TO AMBIENT,
θ
JA
35°C/W
120°C/W
3
2
V
REF
N.C.
V
CC
V
C
OUT UT
GND
WR GND
95°C/W
65°C/W
165°C/W
120°C/W
130°C/W
80°C/W
80°C/W
145°C/W
D PACKAGE
(Top View)
COM
N.C.
V
FB
N.C.
I
SENSE
N.C.
R
T
/C
T
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
REF
N.C.
V
CC
V
C
OUT UT
GROUND
OWER GND
J & N PACKAGE
(Top View)
1. COM
2. V
FB
3. I
SENSE
4. R
T
/C
T
5. OWER GND
1
2
3
4
5
10
9
8
7
6
10.V
REF
9. V
CC
8. V
C
7. OUT UT
6. GND
F PACKAGE
(Top View)
1 20 19
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.
4
5
6
7
8
18
17
16
15
14
9 10 11 12 13
1. N.C.
2. N.C.
3. COM .
4. N.C.
5. V
FB
6. N.C.
7. I
SENSE
8. R
T
/C
T
9. N.C.
10. N.C.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
N.C.
WR GND
GND
N.C.
OUT UT
N.C.
V
C
V
CC
N.C.
V
REF
L PACKAGE
(Top View)
2
Copyright © 2000
Rev. 1.4 4/00
PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
C
URRENT
-M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
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
Parameter
Supply Voltage Range
Output Current (Peak)
Output Current (Continuous)
Analog Inputs (Pin 2, Pin 3)
Error Amp Output Sink Current
Oscillator Frequency Range
Oscillator Timing Resistor
Oscillator Timing Capacitor
Operating Ambient Temperature Range:
SG1844/45
SG2844/45
SG3844/45
Note 3. Range over which the device is functional.
(Note 3)
Symbol
Recommended Operating Conditions
Min.
Typ.
Max.
30
±1
200
0
5
0.1
0.52
0.1
-55
-25
0
2.6
500
150
1.0
125
85
70
Units
V
A
mA
V
mA
kHz
kΩ
µF
°C
°C
°C
R
T
C
T
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG1844/SG1845 with -55°C
≤
T
A
≤
125°C, SG2844/
SG2845 with -25°C
≤
T
A
≤
85°C, SG3844/SG3845 with 0°C
≤
T
A
≤
70°C, V
CC
= 15V (Note 7), R
T
= 10kΩ, and C
T
= 3.3nF. Low duty cycle pulse testing
techniques are used which maintains junction and case temperatures equal to the ambient temperature.)
Parameter
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Stability (Note 4)
Total Output Variation (Note 4)
Output Noise Voltage (Note 4)
Long Term Stability (Note 4)
Output Short Circuit
Symbol
Test Conditions
SG1844/45
SG2844/45
SG3844/45
Units
Min. Typ. Max. Min. Typ. Max. Min. Typ. Max.
4.95 5.00 5.05 4.95 5.00 5.05 4.90 5.00 5.10
6
20
6
20
6
20
6
25
6
25
6
25
0.2 0.4
0.2 0.4
0.2 0.4
4.90
5.10 4.90
5.10 4.82
5.18
50
50
50
5
25
5
25
5
25
-30 -100 -180 -30 -100 -180 -30 -100 -180
47
52
.02
5
1.7
8.3
57
1
47
52
0.2
5
1.7
8.4
57
1
47
52
0.2
5
1.7
8.4
57
1
V
mV
mV
mV/°C
V
µV
mV
mA
kHz
%
%
V
mA
mA
V
µA
dB
MHz
dB
mA
mA
V
V
T
J
= 25°C, I
O
= 1mA
12
≤
V
IN
≤
25V
1
≤
I
O
≤
20mA
Line, Load, Temp.
10Hz
≤
f
≤
10kHz, T
J
= 25°C
T
A
= 125°C, 1000hrs
V
N
Oscillator Section
Initial Accuracy (Note 8)
Voltage Stability
Temperature Stability (Note 4)
Amplitude
Discharge Current
T
J
= 25°C
12V
≤
V
CC
≤
25V
T
MIN
≤
T
A
≤
T
MAX
V
RT/CT
(Peak to Peak)
T
J
= 25°C
T
MIN
≤
T
A
≤
T
MAX
V
COMP
= 2.5V
A
VOL
PSRR
2
≤
V
O
≤
4V
T
J
= 25°C
12
≤
V
CC
≤
25V
V
VFB
= 2.7V, V
COMP
= 1.1V
V
VFB
= 2.3V, V
COMP
= 5V
V
VFB
= 2.3V, R
L
= 15K to gnd
V
VFB
= 2.7V, R
L
= 15K to V
REF
7.8
6.8
9.1
9.3
7.5
7.2
9.3
9.5
7.5
7.2
9.3
9.5
Error Amp Section
Input Voltage
Input Bias Current
Open Loop Gain
Unity Gain Bandwidth (Note 4)
Power Supply Rejection Ratio
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
2.45 2.50 2.55 2.45 2.50 2.55 2.42 2.50 2.58
-0.3 -1
-0.3
1
-0.3 -2
65
90
65
90
65
90
0.7
1
0.7
1
0.7
1
60
70
60
70
60
70
2
6
2
6
2
6
-0.5 -0.8
-0.5 -0.8
-0.5 -0.8
5
6
5
6
5
6
0.7 1.1
0.7 1.1
0.7 1.1
(Electrical Characteristics continue next page.)
Copyright © 2000
Rev. 1.4 4/00
3
PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
C
URRENT
-M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
ELECTRICAL CHARACTERISTICS
Parameter
Current Sense Section
Gain (Notes 5 & 6)
Maximum Input Signal (Note 5)
Power Supply Rejection Ratio (Note 5) PSRR
Input Bias Current
Delay to Output (Note 4)
V
COMP
= 5V
12
≤
V
CC
≤
25V
2.85
0.9
3
1
70
-2
150
0.1
1.5
13.5
13.5
50
50
16
8.4
10
7.6
48
(Cont'd.)
Symbol
Test Conditions
SG1844/45
SG2844/45
SG3844/45
Units
Min. Typ. Max. Min. Typ. Max. Min. Typ. Max.
3.15 2.85
1.1 0.9
-10
300
0.4
2.2
13
12
150
150
17
9.0
11
8.3
50
0
1
17
15
7.8
9
7.0
46
3
1
70
-2
150
0.1
1.5
13.5
13.5
50
50
16
8.4
10
7.6
48
3.15 2.85
1.1 0.9
-10
300
0.4
2.2
13
12
150
150
17
9.0
11
8.2
50
0
14.5
7.8
8.5
7.0
46
3
1
70
-2
150
0.1
1.5
13.5
13.5
50
50
16
8.4
10
7.6
48
3.15
1.1
-10
300
0.4
2.2
V/V
V
dB
µA
ns
V
V
V
V
ns
ns
V
V
V
V
%
%
Output Section
Output Low Level
Output High Level
Rise Time (Note 4)
Fall Time (Note 4)
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
T
J
= 25°C, C
L
= 1nF
T
J
= 25°C, C
L
= 1nF
1844
1845
1844
1845
13
12
150
150
17.5
9.0
11.5
8.2
50
0
Under-Voltage Lockout Section
Start Threshold
Min. Operation Voltage After Turn-On
15
7.8
9
7.0
46
PWM Section
Maximum Duty Cycle
Minimum Duty Cycle
Power Consumption Section
Start-Up Current
Operating Supply Current
V
CC
Zener Voltage
V
FB
= V
ISENSE
= 0V
I
CC
= 25mA
0.5
1
0.5
1
mA
11
17
11
17
mA
34
34
V
∆
V
6. Gain defined as: A =
∆
V
COMP
; 0
≤
V
ISENSE
≤
0.8V.
ISENSE
7. Adjust V
CC
above the start threshold before setting at 15V.
8. Output frequency equals one half of oscillator frequency.
0.5
11
34
Notes: 4. These parameters, although guaranteed, are not 100% tested in
production.
5. Parameter measured at trip point of latch with V
VFB
= 0.
4
Copyright © 2000
Rev. 1.4 4/00
PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
C
URRENT
-M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
BLOCK DIAGRAM
V
CC
*
34V
UVLO
S/R
5V
REF
GROUND**
16V (1844)
8.4 (1845)
2.5V
6V (1844)
0.8V (1845)
V
REF
5.0V
50mA
INTERNAL
BIAS
V
REF
GOOD LOGIC
R
T
/C
T
OSCILLATOR
T
ERROR AMP
V
C
*
OUTPUT
2R
R
1V
S
R
CURRENT SENSE
COMPARATOR
PWM
LATCH
POWER GROUND**
V
FB
COMP
CURRENT SENSE
* - V
CC
and V
C
are internally connected for 8-pin packages.
** - POWER GROUND and GROUND are internally connected for 8-pin packages.
Copyright © 2000
Rev. 1.4 4/00
5
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