AMC DOC. #: AMC3842B_C (LF)
March 2004
®
AMC3842B/43B
C
URRENT
M
ODE
PWM C
ONTROLLER
FEATURES
A
DD MICROTECH CORP.
DESCRIPTION
The AMC3842B/43B are fixed frequency current-mode
PWM controllers specially designed for OFF-Line switching
power supply and DC-to-DC converters with a minimum
number of external components. These devices feature a
trimmed oscillator for precise duty cycle control, a
temperature compensated reference, high gain error
amplifier, current sensing comparator, and high current
totem pole output which is suitable for driving MOSFETs.
The under voltage lock-out (U.V.L.O.) is designed to
operated with 200µA typ. start-up current, allowing an
efficient bootstrap supply voltage design. The U.V.L.O.
thresholds for the AMC3842B are 16V (on) and 10V (off)
which are ideal for off-line applications. The corresponding
typical threshold for the AMC3843B are 8.4V (on) and 7.6V
(off). The AMC3842B/43B can operated within 100% duty
cycle.
APPLICATIONS
Low Start-Up current ( typ. 200
µA)
Optimized for Off-Line and
DC-to-DC Converters
Maximum Duty Cycle
U.V.L.O. with Hysteresis
Operating Frequency Up to 500KHz
Internal Trimmed Bandgap Reference
High Current Totem Pole Output
Error Amplifier With Low Output
Resistance
Available in 8-Pin Plastic DIP and
Surface Mount 14-Pin S.O.I.C.
Identical pin assignment to earlier
UC384X series.
PACKAGE PIN OUT
COMP
V
FB
I
SENSE
R
T
/C
T
V
REF
V
CC
OUTPUT
GND
Off-line flyback or forward
converters.
DC-to-DC buck or boost
converter.
Monitor Power Supply
AVAILABLE OPTIONS
Device
AMC3842B
AMC3843B
Start-UP
Max. Duty
Hysteresis
Voltage
Cycle
16V
8.4V
6V
0.8V
< 100%
< 100%
COMP
NC
V
FB
NC
I
SENSE
NC
R
T
/C
T
8-Pin Plastic DIP
(Top View)
V
REF
NC
V
CC
V
C
OUTPUT
GND
PWR
R
T
/C
T
COMP
V
FB
I
SENSE
V
REF
V
CC
OUTPUT
GND
14-Pin Plastic S.O.I.C.
Surface Mount
(Top View)
ORDER INFORMATION
8-Pin Plastic S.O.I.C.
Surface Mount
(Top View)
Plastic DIP-8
Plastic SO-14
Plastic SO-8
D
DM
8-pin
14-pin
8-pin
0 to 70
AMC384XBM
AMC384XBD
AMC384XBDM
0 to 70
AMC384XBMF(Lead Free) AMC384XBDF(Lead Free)
AMC384XBDMF(Lead Free)
Note: 1.All surface-mount packages are available in Tape & Reel. Append the letter “T” to part number (i.e.
AMC384XBDT, or AMC384XBDMT).
2.The letter ”F” is marked for Lead Free process.
T
A
(
O
C)
M
Copyright
©
2002, ADD Microtech Corp.
1
www.addmtek.com
AMC DOC. #: AMC3842B_C (LF)
March
2004
AMC3842B/43B
C
URRENT
M
ODE
PWM C
ONTROLLER
(Note 1)
ABSOLUTE MAXIMUM RATINGS
35V
Supply voltage, V
CC
Output current, I
O
±
1A
-0.3V to 6.3V
Analog inputs, V
I
10mA
Error amp output sink current, I
SINK(EA)
O
1W
Power dissipation (T
A
= 25 C), P
D
150
O
C
Maximum juncture temperature, T
J
Storage temperature range
-65
O
C to 150
O
C
Lead temperature (soldiering, 10 seconds)
260
O
C
Note 1: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground.
Currents are positive into, negative out of the specified terminal.
THERMAL DATA
M PACKAGE:
Thermal Resistance-Junction to Ambient,
θ
JA
D PACKAGE:
Thermal Resistance-Junction to Ambient,
θ
JA
DM PACKAGE:
Thermal Resistance-Junction to Ambient,
θ
JA
Junction Temperature Calculation: T
J
= T
A
+ (P
D
× 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.
95
O
C/W
120
O
C/W
165
O
C/W
Copyright
©
2002, ADD Microtech Corp.
2
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AMC DOC. #: AMC3842B_C (LF)
March
2004
AMC3842B/43B
C
URRENT
M
ODE
PWM C
ONTROLLER
BLOCK DIAGRAM
7 (12)
V
CC
Internal
Bias
U.V.L.O.
5V
EN
V
REF
36V
V
REF
8 (14)
5 (9)
GND
V
REF
Good Logic
7 (11)
PWR
Error Amp
2R
R
1
V
Current
Sense
R
PWM
Latch
V
C
V
FB
2 (3)
OUTPUT
COMP
1 (1)
S
6 (10)
3 (5)
T
Oscillator
CURRENT
SENSE
R
T
/C
T
4 (7)
PWR
5 (8)
GND
( ) are 14 Pin S.O.I.C. pin number
Note 2
Note 3
Note 4
Note 5
:V
CC
and PWR V
C
are internally connected for 8 pin packages.
:PWR GND and GND are internally connected for 8 pin packages.
:U.V.L.O. is 16V for 3842B and 8.4V for 3843B.
:Hysteresis is 6V for 3842B and 0.8V for 3843B.
Copyright
©
2002, ADD Microtech Corp.
3
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AMC DOC. #: AMC3842B_C (LF)
March
2004
AMC3842B/43B
C
URRENT
M
ODE
PWM C
ONTROLLER
Supply Voltage
Input Voltage
RECOMMENDED OPERATING CONDITIONS
Recommended Operating Conditions
Parameter
Symbol
Min.
Typ.
Max.
V
CC
/ V
C
30
V
I
,R
T
/C
T
V
I
,I
SENSE
/V
FB
V
O
, Output
I
CC
I
O
I
O(REF)
C
T
f
OSC
T
A
0
0
5.5
30
25
200
-20
100
0
500
70
Units
V
V
V
mA
mA
mA
nF
KHz
O
C
Output Voltage
Supply Current
Average Output Current
Reference Output Current
Timing Capacitor
Oscillator Frequency
Operating Free-air Temperature
1
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, these specifications apply over the operating ambient temperature for AMC384XB with
0
O
C
≤
TA
≤70
O
C; V
CC
= 15V(note 6); R
T
= 10K;C
T
= 3.3nF. Low duty cycle pulse testing techniques are used which
maintains junction and case temperatures equal to the ambient temperature.
AMC384XB
Parameter
Symbol
Test Conditions
Units
Min. Typ. Max.
Reference Section
Reference output Voltage
V
REF
Line Regulation
Load Regulation
Short Ciruit Output Current
I
SC
Oscillator Section
Oscillation Frequency
f
Frequency Change with Voltage
Frequency Change with Temperature
(note 7)
Peak-to-peak Amplitude At R
T
/C
T
V
OSC
Current Sense Section
Gain (note 8 & 9)
A
VOL
Maximum Input Signal (note 8)
V
I(MAX)
Power Supply Rejection Ratio (note 8) PSRR
Input Bias Current
I
BIAS
T
J
= 25
O
C, I
REF
= 1mA
12V
≤
V
CC
≤
25V,T
J
= 25
O
C
1mA
≤
I
REF
≤
20mA
T
J
= 25
O
C
T
J
= 25
O
C
12V
≤
V
CC
≤
25V
T
MIN
≤
T
A
≤
T
MAX
4.9
5.0
6
6
-100
52
0.2
5
1.7
2.85
0.9
3.00
1.0
70
-3.0
3.15
1.1
-10
5.1
20
25
-180
V
mV
mV
mA
KHz
%
%
V
V/V
V
dB
µA
-30
1.0
COMP = 5V
12V
≤
V
CC
≤
25V (note 8)
Copyright
©
2002, ADD Microtech Corp.
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AMC DOC. #: AMC3842B_C (LF)
March
2004
AMC3842B/43B
C
URRENT
M
ODE
PWM C
ONTROLLER
ELECTRICAL CHARACTERISTICS (Continued)
Error Amplifier Section
Input Bias Current
Input Voltage
Open Loop Voltage Gain
Unity Gain Bandwidth (note 7)
Power Supply Rejection Ratio
Output Sink Current
Output Source Current
High Output Voltage
Low Output Voltage
Output Section
Output Low Level
Output High Level
Rise Time (note 7)
Fall Time (note 7)
Under-Voltage Lockout Section
Start Threshold
Min. Operating Voltage
PWM Section
I
BIAS
V
I(EA)
G
VO
UGBW
PSRR
I
SINK
I
SOURCE
V
OH
V
OL
COMP = 2.5V
2.42
65
2V
≤
V
O
≤
4V
T
J
= 25
O
C
0.7
60
12V
≤
V
CC
≤
25V
V
FB
= 2.7V, COMP = 1.1V
2
V
FB
= 2.3V, COMP = 5.0V
-0.5
V
FB
= 2.3V, R
L
= 15KΩ to GND 5
V
FB
= 2.7V, RL = 15KΩ to V
REF
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
T
J
= 25
O
C, C
L
= 1nF
T
J
= 25
O
C, C
L
= 1nF
AMC3842B
AMC3843B
AMC3842B
AMC3843B
AMC3842B/43B
AMC3842B
AMC3843B
V
FB
= I
SENSE
= 0V
I
CC
= 25mA
-0.1
2.50
90
1
70
7
-1.0
6
0.7
0.1
1.4
13.5
13.0
50
50
16.0
8.4
10
7.6
97
0.2
0.5
14
35
-2
2.58
1.1
0.4
2.2
µA
V
dB
MHz
dB
mA
mA
V
V
V
OL
V
OH
t
r
t
f
V
V
13
12
150
150
17.5
9.0
11.5
8.2
100
0.35
1.0
17
ns
ns
V
TH(ST)
14.5
7.8
8.5
7.0
94
V
V
Maximum Duty Cycle
Total Standby Current
Startup Current
Operating Supply Current
Zener Voltage
note 6:
note 7:
note 8:
note 9:
I
CC
V
Z
%
mA
mA
V
30
Adjust V
CC
above the start threshold before setting at 15V
These parameters, although guaranteed, are not 100% tested in production prior to shipment
Parameters are measured at trip point of latch with V
FB
= 2V
Gain is measured between I
SENSE
and COMP with the input changing from 0V to 0.8V
Copyright
©
2002, ADD Microtech Corp.
5
www.addmtek.com
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