CM3842/3843

CM3842/3843
CURRENT MODE PWM CONTROLLER
GENERAL DESCRIPTION
FEATURES
The CM3842/43 are fixed frequency current-mode PWM !
Low Start-Up current ( typ. 200µA)
controllers specially designed for OFF-Line switching !
Optimized for Off-Line and DC-to-DC Converters
power supply and DC-to-DC converters with a minimum !
Maximum Duty Cycle
number of external components. These devices feature !
U.V.L.O. with Hysteresis
a trimmed oscillator for precise duty cycle control, a !
Operating Frequency Up to 500KHz
temperature compensated reference, high gain error !
Internal Trimmed Bandgap Reference
amplifier, current sensing comparator, and high current !
High Current Totem Pole Output
totem
pole output which is
suitable
for driving !
!
MOSFETs.
The under voltage lock-out (U.V.L.O.) is designed to
Error Amplifier With Low Output Resistance
Available in 8-Pin Plastic DIP and Surface Mount
8-Pin S.O.I.C.
operated with 200µA 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.
PIN CONFIGURATION
APPLICATIONS
!
Off-line flyback or forward converters.
!
DC-to-DC buck or boost converter.
!
Monitor Power Supply
VREF
COMP
VCC
VFB
ISENSE
OUTPUT
RT/CT
GND
8-Pin PDIP
(Top View)
AVAILABLE OPTIONS
Device
CM3842
Start-UP
Voltage
Hysteresis Max. Duty Cycle
16V
6V
< 100%
COMP
VFB
ISENSE
RT/CT
CM3843
8.4V
0.8V
VREF
VCC
OUTPUT
GND
< 100%
8-Pin S.O.I.C.
(Top View)
2001/06/27 Advanced
Champion Microelectronic Corporation
Page 1
CM3842/3843
CURRENT MODE PWM CONTROLLER
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
7
Internal
Bias
36V
U.V.L.O.
VREF
5V
EN
VREF
8
VCC
5 GND
VREF
Good Logic
7
Error Amp
VFB
Current
Sense
C
2R
2
R
1V
PWM
Latch
R
COMP 1
PWR
VC
OUTPUT
6
S
CURRENT
SENSE
RT/CT
3
4
T
PWR
5 GND
Oscillator
Note 1 :VCC and PWR VC 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.
2001/06/27 Advanced
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Page 2
CM3842/3843
CURRENT MODE PWM CONTROLLER
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
35V
Output current, IO
± 1A
Analog inputs, VI
-0.3V to 6.3V
Error amp output sink current, ISINK(EA)
10mA
O
Power dissipation (TA = 25 C), PD
1W
Maximum junction temperature TJ
150 C
Storage temperature range
-65OC to 150OC
Lead temperature (soldiering, 10 seconds)
260 C
Note 5:
O
O
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, θJA
95 OC/W
SOIC PACKAGE:
Thermal Resistance-Junction to Ambient, θJA
Junction Temperature Calculation:
O
165 C/W
TJ = TA + (PD × θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow.
2001/06/27 Advanced
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Page 3
CM3842/3843
CURRENT MODE PWM CONTROLLER
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Recommended Operating
Min.
Supply Voltage
Typ.
Max.
VCC / VC
VI,RT/CT
Input Voltage
Units
30
V
0
5.5
V
0
30
V
VI,ISENSE/VFB
Output Voltage
VO, Output
Supply Current
ICC
25
mA
Average Output Current
IO
200
mA
IO(REF)
-20
mA
Reference Output Current
Timing Capacitor
CT
Oscillator Frequency
fOSC
Operating Free-air Temperature
TA
1
nF
100
500
0
KHz
O
70
C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, these specifications apply over the operating ambient temperature for CM384X with 0 C ≤
O
TA ≤70 C; VCC = 15V(note 7); RT = 10K;CT = 3.3nF. Low duty cycle pulse testing techniques are used which
O
maintains junction and case temperatures equal to the ambient temperature.
CM384X
Parameter
Symbol
Test Conditions
Units
Min.
Typ.
Max.
4.9
5.0
5.1
V
6
20
mV
6
25
mV
-100
-180
mA
Reference Section
Reference output Voltage
O
VREF
TJ = 25 C, IREF = 1mA
12V ≤ VCC ≤ 25V,TJ = 25 C
O
Line Regulation
1mA ≤ IREF ≤ 20mA
Load Regulation
Short Ciruit Output Current
O
-30
O
47
ISC
TJ = 25 C
f
TJ = 25 C
Oscillator Section
Oscillation Frequency
52
57
KHz
Frequency Change with Voltage
12V ≤ VCC ≤ 25V
0.2
1.0
%
Frequency Change with Temperature
TMIN ≤ TA ≤ TMAX
5
%
1.7
V
(note 8)
Peak-to-peak Amplitude At RT/CT
VOSC
Current Sense Section
Gain (note 9 & 10)
AVOL
Maximum Input Signal (note 9)
VI(MAX)
COMP = 5V
Power Supply Rejection Ratio (note 9)
PSRR
12V ≤ VCC ≤ 25V (note 9)
Input Bias Current
2001/06/27 Advanced
2.85
3.00
3.15
0.9
1.0
1.1
IBIAS
70
-3.0
Champion Microelectronic Corporation
V/V
V
dB
-10
µA
Page 4
CM3842/3843
CURRENT MODE PWM CONTROLLER
ELECTRICAL CHARACTERISTICS (Continued)
Error Amplifier Section
Input Bias Current
IBIAS
Input Voltage
VI(EA)
COMP = 2.5V
GVO
2V ≤ VO ≤ 4V
Open Loop Voltage Gain
-0.1
-2
µA
2.42
2.50
2.58
V
65
90
dB
Unity Gain Bandwidth (note 8)
UGBW
TJ = 25 C
0.7
1
MHz
Power Supply Rejection Ratio
PSRR
12V ≤ VCC ≤ 25V
60
70
dB
ISINK
VFB = 2.7V, COMP = 1.1V
2
7
mA
ISOURCE
VFB = 2.3V, COMP = 5.0V
-0.5
-1.0
mA
5
6
V
Output Sink Current
Output Source Current
O
High Output Voltage
VOH
VFB = 2.3V, RL = 15KΩ to GND
Low Output Voltage
VOL
VFB = 2.7V, RL = 15KΩ to VREF
0.7
1.1
ISINK = 20mA
0.1
0.4
ISINK = 200mA
1.4
2.2
V
Output Section
Output Low Level
Output High Level
VOL
VOH
ISOURCE = 20mA
13
13.5
ISOURCE = 200mA
12
13.0
V
V
O
50
150
ns
O
50
150
ns
Rise Time (note 8)
tr
TJ = 25 C, CL = 1nF
Fall Time (note 8)
tf
TJ = 25 C, CL = 1nF
Under-Voltage Lockout Section
Start Threshold
VTH(ST)
Min. Operating Voltage
CM3842
14.5
16.0
17.5
CM3843
7.8
8.4
9.0
CM3842
8.5
10
11.5
CM3843
7.0
7.6
8.2
CM3842/43
94
97
100
V
V
PWM Section
Maximum Duty Cycle
Minimum Duty Cycle
0
%
%
Total Standby Current
Startup Current
CM3842
0.2
0.35
CM3843
0.5
1.0
14
17
Operating Supply Current
ICC
VFB = ISENSE = 0V
Zener Voltage
VZ
ICC = 25mA
30
35
note 7:
Adjust VCC 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 VFB = 2V
mA
mA
V
note 10: Gain is measured between ISENSE and COMP with the input changing from 0V to 0.8V
2001/06/27 Advanced
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Page 5
CM3842/3843
CURRENT MODE PWM CONTROLLER
APPLICATION INFORMATION
Error
Amp
2R
R
1V
COMP
Rf
RS
ISENSE
Cf
Current
Sense
Comparator
GND
Fig. 1. Current Sense Circuit
Peak current (IS) is set by: IS(MAX) = 1V/RS
VREF
2.5V
Error
Amp
0.5mA
RT
RT/CT
VFB
Zi
CT
Zf
GND
COMP
Fig. 3. Oscillator Section
1.72
For RT < 5K, f =
RTCT
Fig. 2. Error Amplifier Configuration - the
amplifier can source or sink up to 0.5mA
VREF
RT
4.7K
VCC
2N2222
100K
1K
Error AMP
Adjust
4.7K
5K
ISENSE
Adjust
COMP
VREF
VFB
VCC
0.1µ
µF
1K,
1W
Output
ISENSE Output
RT/CT
GND
0.1µ
µF
GND
CT
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 ISENSE pin
2001/06/27 Advanced
Champion Microelectronic Corporation
Page 6
CM3842/3843
CURRENT MODE PWM CONTROLLER
APPLICATION INFORMATION (continued)
1K
COMP
VREF
Shutdown
330Ω
Ω
ISENSE
Shutdown
500Ω
Ω
To Current
Sense Resistor
Fig. 5. Shutdown Techniques - there are two ways to shutdown the PWM controller: 1) raise the voltage at
ISENSE above 1V or, 2) pull the COMP below a voltage two diodes above ground.
VREF
0.1µ
µF
RT
RT/CT
CT
ISENSE
R2
R1
ISENSE
RSENSE
C
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.
2001/06/27 Advanced
Champion Microelectronic Corporation
Page 7
CM3842/3843
CURRENT MODE PWM CONTROLLER
TYPICAL CHARACTERISTICS
f-oscillator frequency and frequency variation
Oscillator Frequency and Frequemcy Variation
1,000,000
100,000
1uF
0.1uF
0.01uF
0.001uF
10,000
1,000
100
10
1
10
100
1000
RT-Timing Resistance (unit: k ohm)
2001/06/27 Advanced
Champion Microelectronic Corporation
Page 8
CM3842/3843
CURRENT MODE PWM CONTROLLER
8-PIN PLASTIC DIP
5
8
INCHES
MILLIMETERS
B
MIN
1
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
4
A
L
F
C
G
-
-
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.
J
K
H
C
M
D
M
-
7º
7.62 BSC.
15º
-
7º
15º
8-PIN PLASTIC S.O.I.C
.
INCHES
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
-
0.035
0.38
-
0.89
A
B
P
F
D
G
C
SEATING PLAN
K
2001/06/27 Advanced
M
J
0.015
G
L
MILLIMETERS
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
-
-
8º
-
-
8º
P
0.228
-
0.244
5.79
-
6.20
Champion Microelectronic Corporation
Page 9
CM3842/3843
CURRENT MODE PWM CONTROLLER
8-PIN PLASTIC S.O.I.C. CARRIER DIMENSIONS
D
T2
MILLIMETERS
C
A
330 ± 1
DD
1.55 ± 0.1
B
100 ± 1
D1
1.5 ± 0.25
Po
4.0 ± 0.1
B A
+0.5
C
13.0
-1.0
T1
DD
E
Po
F
D1
P
Ao
2001/06/27 Advanced
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
Ko
2.1 ± 0.1
t
0.30 ± 0.013
Wc
P1
Wc
D
t
Wt
Wt
9.3 TYP.
P
8.0 ± 0.1
E
1.75 ± 0.1
F
5.5 ± 0.1
Bo
Ko
12.0
+0.3
-0.1
Champion Microelectronic Corporation
Page 10
CM3842/3843
CURRENT MODE PWM CONTROLLER
IMPORTANT NOTICE
Champion Microelectronic Corporation (CMC) reserves the right to make changes to its products or to discontinue any
integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant
information to verify, before placing orders, that the information being relied on is current.
A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe
property or environmental damage.
CMC integrated circuit products are not designed, intended, authorized, or
warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of
CMC products in such applications is understood to be fully at the risk of the customer. In order to minimize risks
associated with the customer’s applications, the customer should provide adequate design and operating safeguards.
CMC assumes to no liability to customer product design or application support. CMC warrants the performance of its
products to the specifications applicable at the time of sale.
HsinChu Headquarter
Sales & Marketing
5F, No. 11, Park Avenue II,
Science-Based Industrial Park,
HsinChu City, Taiwan
T E L : +886-3-5679979
FA X : +886-3-5679909
11F, No. 306-3, SEC. 1, Ta Tung Road,
Hsichih, Taipei Hsien 221, Taiwan
2001/06/27 Advanced
T E L : +886-2-86921591
FA X : +886-2-86921596
Champion Microelectronic Corporation
Page 11