SG1844/SG1845/SG3844/SG3845
Current Mode PWM Controller
Description
The SG1844/45 family of control ICs provides all the
required 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 SG3844/45 is designed for the commercial
range of 0°C to 70°C.
Features
Optimized for Off-Line Control
Low Start-Up Current (<1mA)
Automatic Feed Forward Compensation
Trimmed Oscillator
Discharge Current
Pulse-By-Pulse Current Limiting
Enhanced Load Response Characteristics
Undervoltage Lockout with 6V Hysteresis
(SG1844 only)
Double Pulse Suppression
High-Current Totem-Pole Output
Internally Trimmed Bandgap Reference
500kHz Operation
Under-voltage Lockout
SG1844 - 16 Volts
SG1845 - 8.4 Volts
Low Shoot-through Current <75mA Over
Temperature
Application
Available to MIL-STD-883
Available to DSCC
– Standard Microcircuit Drawing (SMD)
SGR1844/45 Rad-Tolerant Version Available
Product Highlight
R
ST
I
ST
V
cc
AC
INPUT
SG3844
Figure 1 ·
Product Highlight
November 2014 Rev. 1.7
www.microsemi.com
© 2014 Microsemi Corporation- Analog Mixed Signal Group
1
Current Mode PWM Controller
Connection Diagrams and Ordering Information
Ambient
Temperature
Type
Package
Part Number
Packaging
Type
COM
V
FB
I
SENSE
R
T
/C
T
Connection Diagram
V
REF
V
CC
OUTPUT
GND
SG3844M
0°C to 70°C
M
8-PIN PLASTIC
DUAL INLINE
PACKAGE
SG3845M
PDIP
M PACKAGE
(Top View)
M Package:
RoHS / Pb-free 100% Matte Tin Lead Finish
SG1844Y
SG1845Y
-55°C to
125°C
8-PIN
CERAMIC
DUAL INLINE
PACKAGE
SG1844Y-883B
CERDIP
SG1845Y-883B
SG1844Y-DESC
SG1845Y-DESC
COM
V
FB
I
SENSE
R
T
/C
T
V
REF
V
CC
OUTPUT
GND
Y
Y PACKAGE
(Top View)
PbSn Tin Lead Finish
COM
V
REF
V
CC
OUTPUT
GND
0°C to 70°C
DM
8-PIN SMALL
OUTLINE
INTEGRATED
CIRCUIT
SG3844DM
SOIC
SG3845DM
V
FB
I
SENSE
R
T
/C
T
DM PACKAGE
(Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
COM
N.C.
V
REF
N.C.
V
CC
V
C
OUT UT
GND
WR GND
SG3844D
0°C to 70°C
D
14-PIN SMALL
OUTLINE
INTEGRATED
CIRCUIT
SG3845D
SOIC
V
FB
N.C.
I
SENSE
N.C.
R
T
/C
T
D PACKAGE
(Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
2
Connection Diagrams and Ordering Information
Ambient
Temperature
Package
Part Number
SG1844J
SG1845J
Packaging
Type
Connection Diagram
COM
N.C.
V
FB
N.C.
I
SENSE
N.C.
R
T
/C
T
V
REF
N.C.
V
CC
V
C
OUTPUT
GND
PGND
-55°C to
125°C
J
14-PIN
CERAMIC
DUAL INLINE
PACKAGE
SG1844J-883B
SG1845J-883B
SG1844J-DESC
SG1845J-DESC
CERDIP
J PACKAGE
(Top View)
PbSn
Lead Finish
-55°C to
125°C
F
10-PIN
CERAMIC
FLAT PACK
PACKAGE
SG1844F-DESC
FLAT PACK
SG1845F-DESC
COM
V
FB
I
SENSE
R
T
/C
T
PGND
V
REF
V
CC
V
C
OUTPUT
GND
F PACKAGE
(Top View)
PbSn Lead Finish
SG1844L
3
2
1 20 19
18
17
16
15
14
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.
GND
N.C.
OUT UT
SG1845L
SG1844L-883B
SG1845L-883B
SG1844L-DESC
SG1845L-DESC
Ceramic
(LCC)
Leadless
Chip Carrier
4
5
6
7
8
N.C.
Vc
Vcc
N.C.
V
REF
-55°C to
125°C
L
20-Pin
CERAMIC
9 10 11 12 13
L PACKAGE
(Top View)
PbSn Lead Finish
Notes:
1. Contact factory for DESC part availability.
2. All parts are viewed from the top.
3. Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. SG3844D-TR)
4. Hermetic Packages J, F, L, & Y use Pb37/Sn63 hot solder lead finish, contact factory for availability of RoHS versions.
3
Current Mode PWM Controller
Absolute Maximum Ratings
1 - 2
Parameter
Supply Voltage (Low Impedance Source)
Output Current (Peak)
Output Current (Continuous)
Output Energy (Capacitive Load)
Analog Inputs (V
FB
, I
SENSE
)
Error Amplifier Output Sink Current
Operating Junction Temperature
Hermetic (J, Y, F, L Packages)
Plastic (M, D, DM Packages)
Storage Temperature Range
Lead Temperature (Soldering, 10 Seconds)
150
150
-65 to +150
300
°C
°C
°C
°C
°C
Value
30
±1
350
5
-0.3 to +6.3
10
Units
V
A
mA
µJ
V
mA
RoHS / Pb-free Peak Package Solder Reflow Temp. (40 second
260 (+0, -5)
max. exposure)
Notes:
1. Exceeding these ratings could cause damage to the device.
2. All voltages are with respect to Pin 5. All currents are positive into the specified terminal.
Thermal Data
Parameter
M 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 Case, θ
JC
Thermal Resistance-Junction to Ambient, θ
JA
J Package
Thermal Resistance-Junction to Case, θ
JC
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
35
°C/W
°C/W
Thermal Resistance-Junction to Ambient, θ
JA
120
Notes:
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.
80
145
°C/W
°C/W
30
80
°C/W
°C/W
30
130
°C/W
°C/W
120
°C/W
165
°C/W
95
°C/W
Value
Units
4
Recommended Operating Conditions3
Recommended Operating Conditions
3
Symbol
V
S
I
PK
I
OUT
EA
ISNK
OSC
FR
R
T
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
0.1
0.52
0.001
-55
0
0
5
500
150
1.0
125
70
Recommended Operating Conditions
Min.
Typ.
Units
V
A
mA
Max.
30
±1
200
2.6
V
mA
kHz
kΩ
µF
°C
°C
C
T
Oscillator Timing Capacitor
Operating Ambient Temperature Range:
SG1844/45
SG3844/45
Note:
3. Range over which the device is functional.
Electrical Characteristics
Unless otherwise specified, these specifications apply over the operating ambient temperatures for
SG1844/SG1845 with -55°C
≤
T
A
≤
125°C, SG3844/SG3845 with 0°C ≤ T
A
≤ 70°C, VCC = 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.
SG1844/SG1845
Min.
Typ.
Max
SG3844/SG3845
Min.
Typ.
Max
Symbol
Parameter
Test Conditions
Units
Reference Section
V
REF
V
REG
I
REG
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
4
4
T
J
= 25°C, I
O
= 1mA
12V ≤ V
IN
≤ 25V
1 ≤ I
O
≤ 20mA
Line, Load,
Temperature
10Hz ≤ f ≤ 10kHz, T
J
= 25°C
T
A
= 125°C, 1000hrs
4.95
5.00
6
6
0.2
5.05
20
25
0.4
5.10
4.90
5.00
6
6
0.2
5.10
20
25
0.4
5.18
V
mV
mV
mV/°C
V
µV
Total Output Variation
V
N
Output Noise Voltage
Long Term Stability
V
REFISC
4
4.90
50
5
-30
-100
4.82
50
4
25
-180
-30
5
-100
25
-180
mV
mA
Output Short Circuit
Oscillator Section
f
f
REG
OSC
PP
I
DSG
Initial Accuracy
8
T
J
= 25°C
12V ≤ V
CC
≤ 25V
4
47
52
.02
5
1.7
57
1
47
52
0.2
5
1.7
57
1
kHz
%
%
V
Voltage Stability
Temperature Stability
Amplitude
Discharge Current
T
MIN
≤
T
A
≤
T
MAX
V
RT/CT
(Peak to Peak)
T
J
= 25°C
T
MIN
≤
T
A
≤
T
MAX
7.8
6.8
8.3
9.1
9.3
7.5
7.2
8.4
9.3
9.5
mA
mA
5
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