www.docs.chipfind.ru
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 1
GENERAL DESCRIPTION
FEATURES
The CM3842/43 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 200
A typ. start-up current, allowing an
efficient bootstrap supply voltage design. The U.V.L.O.
thresholds for the CM3842 are 16V (on) and 10V (off)
which are ideal for off-line applications. The
corresponding typical threshold for the CM3843 are
8.4V (on) and 7.6V (off). The CM3842/43 can operated
within 100% duty cycle.
!
Low Start-Up current ( typ. 200
A)
!
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
8-Pin S.O.I.C.
APPLICATIONS
PIN CONFIGURATION
!
Off-line flyback or forward converters.
!
DC-to-DC buck or boost converter.
!
Monitor Power Supply
8-Pin PDIP
(Top View)
AVAILABLE OPTIONS
Device
Start-UP
Voltage
Hysteresis Max. Duty Cycle
CM3842 16V 6V
<
100%
CM3843 8.4V 0.8V <
100%
8-Pin S.O.I.C.
(Top View)
COMP
V
FB
I
SENSE
V
REF
GND
OUTPUT
V
CC
R
T
/C
T
COMP
V
FB
I
SENSE
V
REF
GND
OUTPUT
V
CC
R
T
/C
T
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 2
ORDERING INFORMATION
Part Number
Temperature Range
Package
CM3842/43CP
0
to 70
8-Pin PDIP(P08)
CM3842/43CS
0
to 70
8-Pin SOIC(S08)
BLOCK DIAGRAM
Note 1 :V
CC
and PWR V
C
are internally connected for 8 pin packages.
Note 2 :PWR GND and GND are internally connected for 8 pin packages.
Note 3 :U.V.L.O. is 16V for 3842 and 8.4V for 3843.
Note 4 :Hysteresis is 6V for 3842 and 0.8V for 3843.
V
REF
Internal
Bias
36V
2R
EN
5V
V
REF
U.V.L.O.
V
REF
Good Logic
Error Amp
Current
Sense
C
Oscillator
R
1
V
R
S
PWM
Latch
V
FB
CURRENT
SENSE
R
T
/C
T
PWR
GND
OUTPUT
PWR
V
C
GND
V
CC
COMP
T
1
2
3
4
8
5
6
7
5
7
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 3
ABSOLUTE MAXIMUM RATINGS
Supply voltage, V
CC
35V
Output current, I
O
1A
Analog inputs, V
I
-0.3V to 6.3V
Error amp output sink current, I
SINK(EA)
10mA
Power dissipation (T
A
= 25
O
C), P
D
1W
Maximum junction temperature T
J
150
O
C
Storage temperature range
-65
O
C to 150
O
C
Lead temperature (soldiering, 10 seconds)
260
O
C
Note 5: 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
PDIP PACKAGE:
Thermal Resistance-Junction to Ambient,
JA
95
O
C/W
SOIC PACKAGE:
Thermal Resistance-Junction to Ambient,
JA
165
O
C/W
Junction Temperature Calculation: T
J
= T
A
+ (P
D
JA
).
The
JA
numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow.
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 4
RECOMMENDED OPERATING CONDITIONS
Recommended Operating
Parameter Symbol
Min. Typ. Max.
Units
Supply Voltage
V
CC
/ V
C
30 V
V
I
,R
T
/C
T
Input Voltage
V
I
,I
SENSE
/V
FB
0 5.5
V
Output Voltage V
O
, Output 0
30 V
Supply Current
I
CC
25
mA
Average Output Current
I
O
200
mA
Reference Output Current
I
O(REF)
-20
mA
Timing Capacitor C
T
1
nF
Oscillator Frequency
f
OSC
100
500
KHz
Operating Free-air Temperature T
A
0
70
O
C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, these specifications apply over the operating ambient temperature for CM384X with 0
O
C
T
A
70
O
C; V
CC
= 15V(note 7); 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.
CM384X
Parameter Symbol
Test
Conditions
Min. Typ. Max.
Units
Reference Section
Reference output Voltage
V
REF
T
J
= 25
O
C, I
REF
= 1mA
4.9
5.0
5.1
V
Line Regulation
12V
V
CC
25V,T
J
= 25
O
C
6
20
mV
Load Regulation
1mA
I
REF
20mA
6
25
mV
Short Ciruit Output Current
I
SC
T
J
= 25
O
C
-30
-100
-180
mA
Oscillator Section
Oscillation Frequency
f
T
J
= 25
O
C
47
52
57
KHz
Frequency Change with Voltage
12V
V
CC
25V
0.2
1.0
%
Frequency Change with Temperature
(note 8)
T
MIN
T
A
T
MAX
5
%
Peak-to-peak Amplitude At R
T
/C
T
V
OSC
1.7
V
Current Sense Section
Gain (note 9 & 10)
A
VOL
2.85
3.00
3.15
V/V
Maximum Input Signal (note 9)
V
I(MAX)
COMP = 5V
0.9
1.0
1.1
V
Power Supply Rejection Ratio (note 9)
PSRR
12V
V
CC
25V (note 9)
70
dB
Input Bias Current
I
BIAS
-3.0
-10
A
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 5
ELECTRICAL CHARACTERISTICS (Continued)
Error Amplifier Section
Input Bias Current
I
BIAS
-0.1
-2
A
Input Voltage
V
I(EA)
COMP = 2.5V
2.42
2.50
2.58
V
Open Loop Voltage Gain
G
VO
2V
V
O
4V
65
90
dB
Unity Gain Bandwidth (note 8)
UGBW
T
J
= 25
O
C
0.7
1
MHz
Power Supply Rejection Ratio
PSRR
12V
V
CC
25V
60
70
dB
Output Sink Current
I
SINK
V
FB
= 2.7V, COMP = 1.1V
2
7
mA
Output Source Current
I
SOURCE
V
FB
= 2.3V, COMP = 5.0V
-0.5
-1.0
mA
High Output Voltage
V
OH
V
FB
= 2.3V, R
L
= 15K
to GND
5
6
V
Low Output Voltage
V
OL
V
FB
= 2.7V, RL = 15K
to V
REF
0.7
1.1
V
Output Section
I
SINK
= 20mA
0.1
0.4
Output Low Level
V
OL
I
SINK
= 200mA
1.4
2.2
V
I
SOURCE
= 20mA
13
13.5
Output High Level
V
OH
I
SOURCE
= 200mA
12
13.0
V
Rise Time (note 8)
t
r
T
J
= 25
O
C, C
L
= 1nF
50
150
ns
Fall Time (note 8)
t
f
T
J
= 25
O
C, C
L
= 1nF
50
150
ns
Under-Voltage Lockout Section
CM3842
14.5
16.0
17.5
Start Threshold
V
TH(ST)
CM3843
7.8
8.4
9.0
V
CM3842
8.5
10
11.5
Min. Operating Voltage
CM3843
7.0
7.6
8.2
V
PWM Section
CM3842/43
94
97
100
Maximum Duty Cycle
%
Minimum Duty Cycle
0
%
Total Standby Current
CM3842
0.2
0.35
Startup Current
CM3843
0.5
1.0
mA
Operating Supply Current
I
CC
V
FB
= I
SENSE
= 0V
14
17
mA
Zener Voltage
V
Z
I
CC
= 25mA
30
35
V
note 7: Adjust V
CC
above the start threshold before setting at 15V
note 8: These parameters, although guaranteed, are not 100% tested in production prior to shipment
note 9: Parameters are measured at trip point of latch with V
FB
= 2V
note 10: Gain is measured between I
SENSE
and COMP with the input changing from 0V to 0.8V
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 6
APPLICATION INFORMATION
Fig. 1. Current Sense Circuit
Peak current (I
S
) is set by: I
S(MAX)
= 1V/R
S
Fig. 3. Oscillator Section
1.72
Fig. 2. Error Amplifier Configuration - the
amplifier can source or sink up to 0.5mA
For R
T
< 5K, f =
R
T
C
T
Fig. 4. Open-loop laboratory test fixture: Careful grounding techniques are necessary for high peak
currents associated with capacitive loads. Timing and bypass capacitors should be connected to
GND pin in a single point ground. The transistor and 5K potentiometer are used to sample the
oscillator waveform and apply an adjustable ramp to the I
SENSE
pin
GND
I
SENSE
COMP
Error
Amp
R
S
R
f
C
f
R
2R
1V
Current
Sense
Comparator
4.7K
1K
Error AMP
Adjust
4.7K
2N2222
100K
5K
I
SENSE
Adjust
COMP
V
FB
I
SENSE
R
T
/C
T
GND
V
REF
V
CC
Output
0.1
F
Output
1K,
1W
V
CC
V
REF
0.1
F
GND
C
T
R
T
2.5V
Z
f
Z
i
0.5mA
V
FB
COMP
Error
Amp
GND
R
T
/C
T
V
REF
C
T
R
T
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 7
APPLICATION INFORMATION (continued)
Fig. 5. Shutdown Techniques - there are two ways to shutdown the PWM controller: 1) raise the voltage at
I
SENSE
above 1V or, 2) pull the COMP below a voltage two diodes above ground.
Fig 6. Slop Compensation To achieve duty cycles over 50% for some applications , the above
slope compensation technique is suggested by resistively summing a fraction of the
oscillator ramp with the current sense signal.
I
SENSE
Shutdown
V
REF
500
To Current
Sense Resistor
330
1K
Shutdown
COMP
V
REF
R
T
/C
T
I
SENSE
R
T
C
T
0.1
F
C
R
2
R
1
I
SENSE
R
SENSE
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 8
TYPICAL CHARACTERISTICS
Oscillator Frequency and Frequemcy Variation
10
100
1,000
10,000
100,000
1,000,000
1
10
100
1000
RT-Timing Resistance (unit: k ohm)
f-oscillator frequency and frequency variation
1uF
0.1uF
0.01uF
0.001uF
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 9
8-PIN PLASTIC DIP
INCHES MILLIMETERS
MIN TYP MAX MIN TYP MAX
A 0.355 0.365 0.400 9.02 9.27 10.16
B 0.240 0.250 0.280 6.10 6.35 7.11
C - - 0.210 - - 5.33
D - 0.018 - - 0.46 -
F - 0.060 - - 1.52 -
G - 0.100 - - 2.54 -
H
0.050 - 0.090
1.27 - 2.29
J
0.008 - 0.015
0.20 - 0.38
K 0.115 0.130 0.150 2.92 3.30 3.81
L
0.300 BSC.
7.62 BSC.
1
B
5
4
8
C
K
F
H
G
D
A
L
M
J
M - 7 15 - 7 15
8-PIN PLASTIC S.O.I.C
INCHES MILLIMETERS
MIN TYP MAX MIN TYP MAX
A
0.183 - 0.202
4.65 - 5.13
B
0.144 - 0.163
3.66 - 4.14
C
0.068 - 0.074
1.73 - 1.88
D
0.010 - 0.020
0.25 - 0.51
F
0.015 - 0.035
0.38 - 0.89
G
0.050 BSC
0.050 BSC
J
0.007 - 0.010
0.19 - 0.25
K
0.005 - 0.010
0.13 - 0.25
L
0.189 - 0.205
4.80 - 5.21
M - - 8 - - 8
P
0.228 - 0.244
5.79 - 6.20
.
SEATING PLAN
A
D
F
P
B
K
C
M
L
J
G
CM3842/3843
C
URRENT
M
ODE
PWM C
ONTROLLER
2001/06/27
Advanced
Champion Microelectronic Corporation
Page 10
8-PIN PLASTIC S.O.I.C. CARRIER DIMENSIONS
MILLIMETERS
A
330
1
DD
1.55
0.1
B
100
1
D1
1.5
0.25
+0.5
C 13.0
-1.0
Po
4.0
0.1
D
2.2
1
P1
2.0
0.1
T1
12.5
0.5
Ao
6.4
0.1
T2
2.0
0.2
Bo
5.2
0.1
+0.3
Wc 12.0
-0.1
Ko
2.1
0.1
Wt 9.3
TYP. t 0.30
0.013
P
8.0
0.1
E
1.75
0.1
F
5.5
0.1
T2
T1
C
D
D1
B A
E
F
Wc
P
Po
DD
Ao
P1
Ko
Wt
t
Bo
CERAMIC/SURGE
ABSORBER
SHANGHAI,CHINA
DIODES LAB
HANGZHOU,CHINA
CERAMIC/PZT
SHINCHU,TAIWAN
DC POWER LAB
TAIPEI,TAIWAN
Document Outline
PDF 
ZIP