Order this document by UC3842B/D
UC3842B, 43B
UC2842B, 43B
High Performance
Current Mode Controllers
The UC3842B, UC3843B series are high performance fixed frequency
current mode controllers. They are specifically designed for Off–Line and
dc–to–dc converter applications offering the designer a cost–effective
solution with minimal external components. These integrated circuits feature
a trimmed oscillator for precise duty cycle control, a temperature
compensated reference, high gain error amplifier, current sensing
comparator, and a high current totem pole output ideally suited for driving a
power MOSFET.
Also included are protective features consisting of input and reference
undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting,
programmable output deadtime, and a latch for single pulse metering.
These devices are available in an 8–pin dual–in–line and surface mount
(SO–8) plastic package as well as the 14–pin plastic surface mount (SO–14).
The SO–14 package has separate power and ground pins for the totem pole
output stage.
The UCX842B has UVLO thresholds of 16 V (on) and 10 V (off), ideally
suited for off–line converters. The UCX843B is tailored for lower voltage
applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).
•
Trimmed Oscillator for Precise Frequency Control
HIGH PERFORMANCE
CURRENT MODE
CONTROLLERS
N SUFFIX
PLASTIC PACKAGE
CASE 626
D1 SUFFIX
PLASTIC PACKAGE
CASE 751
(SO–8)
D SUFFIX
PLASTIC PACKAGE
CASE 751A
(SO–14)
8
1
8
1
14
1
•
•
•
•
•
•
•
•
Oscillator Frequency Guaranteed at 250 kHz
Current Mode Operation to 500 kHz
Automatic Feed Forward Compensation
Latching PWM for Cycle–By–Cycle Current Limiting
Internally Trimmed Reference with Undervoltage Lockout
High Current Totem Pole Output
Undervoltage Lockout with Hysteresis
Low Startup and Operating Current
Compensation
NC
Voltage Feedback
NC
Current Sense
NC
RT/CT
1
2
3
4
5
6
7
PIN CONNECTIONS
Compensation
Voltage Feedback
Current Sense
RT/CT
1
2
3
4
8
7
6
5
Vref
VCC
Output
Gnd
(Top View)
14
13
12
11
10
9
8
Simplified Block Diagram
VCC
Vref
8(14)
R
R
RT/CT
4(7)
Voltage
Feedback
Input
2(3)
Output
Compensation
1(1)
+
–
7(12)
Vref
NC
VCC
VC
Output
Gnd
Power Ground
(Top View)
5.0V
Reference
Vref
Undervoltage
Lockout
Oscillator
Latching
PWM
Error
Amplifier
6(10)
Power
Ground
5(8)
Current
Sense
3(5) Input
Gnd
5(9)
VCC
Undervoltage
Lockout
VC
7(11)
Output
ORDERING INFORMATION
Operating
Device
Temperature Range
UC384XBD
UC384XBD1
TA = 0° to +70°C
UC384XBN
UC284XBD
TA = – 25° to +85°C
UC284XBD1
UC284XBN
UC384XBVD
UC384XBVD1 TA = – 40° to +105°C
UC384XBVN
Package
SO–14
SO–8
Plastic
SO–14
SO–8
Plastic
SO–14
SO–8
Plastic
Pin numbers in parenthesis are for the D suffix SO–14 package.
X indicates either a 2 or 3 to define specific device part
numbers.
©
Motorola, Inc. 1996
Rev 1
MOTOROLA ANALOG IC DEVICE DATA
1
UC3842B, 43B UC2842B, 43B
MAXIMUM RATINGS
Rating
Total Power Supply and Zener Current
Output Current, Source or Sink (Note 1)
Output Energy (Capacitive Load per Cycle)
Current Sense and Voltage Feedback Inputs
Error Amp Output Sink Current
Power Dissipation and Thermal Characteristics
D Suffix, Plastic Package, SO–14 Case 751A
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance, Junction–to–Air
D1 Suffix, Plastic Package, SO–8 Case 751
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance, Junction–to–Air
N Suffix, Plastic Package, Case 626
Maximum Power Dissipation @ TA = 25°C
Thermal Resistance, Junction–to–Air
Operating Junction Temperature
Operating Ambient Temperature
UC3842B, UC3843B
UC2842B, UC2843B
UC3842BV, UC3843BV
Storage Temperature Range
Symbol
(ICC + IZ)
IO
W
Vin
IO
Value
30
1.0
5.0
– 0.3 to + 5.5
10
Unit
mA
A
µJ
V
mA
PD
R
θJA
PD
R
θJA
PD
R
θJA
TJ
TA
862
145
702
178
1.25
100
+150
0 to + 70
– 25 to + 85
–40 to +105
mW
°C/W
mW
°C/W
W
°C/W
°C
°C
Tstg
– 65 to +150
°C
ELECTRICAL CHARACTERISTICS
(VCC = 15 V [Note 2], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values TA is
the operating ambient temperature range that applies [Note 3], unless otherwise noted.)
UC284XB
Characteristics
REFERENCE SECTION
Reference Output Voltage (IO = 1.0 mA, TJ = 25°C)
Line Regulation (VCC = 12 V to 25 V)
Load Regulation (IO = 1.0 mA to 20 mA)
Temperature Stability
Total Output Variation over Line, Load, and Temperature
Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C)
Long Term Stability (TA = 125°C for 1000 Hours)
Output Short Circuit Current
OSCILLATOR SECTION
Frequency
TJ = 25°C
TA = Tlow to Thigh
TJ = 25°C (RT = 6.2 k, CT = 1.0 nF)
Frequency Change with Voltage (VCC = 12 V to 25 V)
Frequency Change with Temperature
TA = Tlow to Thigh
Oscillator Voltage Swing (Peak–to–Peak)
Discharge Current (VOSC = 2.0 V)
TJ = 25°C
TA = Tlow to Thigh (UC284XB, UC384XB)
TA = Tlow to Thigh
(UC384XBV)
fOSC
49
48
225
∆f
OSC/∆V
∆f
OSC/∆T
VOSC
Idischg
–
–
–
7.8
7.5
–
52
–
250
0.2
1.0
1.6
8.3
–
–
55
56
275
1.0
–
–
8.8
8.8
–
49
48
225
–
–
–
7.8
7.6
7.2
52
–
250
0.2
0.5
1.6
8.3
–
–
55
56
275
1.0
–
–
8.8
8.8
8.8
%
%
V
mA
kHz
Vref
Regline
Regload
TS
Vref
Vn
S
ISC
4.95
–
–
–
4.9
–
–
– 30
5.0
2.0
3.0
0.2
–
50
5.0
– 85
5.05
20
25
–
5.1
–
–
–180
4.9
–
–
–
4.82
–
–
– 30
5.0
2.0
3.0
0.2
–
50
5.0
– 85
5.1
20
25
–
5.18
–
–
–180
V
mV
mV
mV/°C
V
µV
mV
mA
Symbol
Min
Typ
Max
Min
UC384XB, XBV
Typ
Max
Unit
NOTES:
1. Maximum Package power dissipation limits must be observed.
2. Adjust VCC above the Startup threshold before setting to 15 V.
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
Tlow = 0°C for UC3842B, UC3843B
Thigh = +70°C for UC3842B, UC3843B
Tlow =
–25°C for UC2842B, UC2843B
Thigh =
+85°C for UC2842B, UC2843B
Tlow =
–40°C for UC3842BV, UC3843BV
Thigh =
+105°C for UC3842BV, UC3843BV
2
MOTOROLA ANALOG IC DEVICE DATA
UC3842B, 43B UC2842B, 43B
ELECTRICAL CHARACTERISTICS
(VCC = 15 V [Note 2], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values TA is
the operating ambient temperature range that applies [Note 3], unless otherwise noted.)
UC284XB
Characteristics
ERROR AMPLIFIER SECTION
Voltage Feedback Input (VO = 2.5 V)
Input Bias Current (VFB = 5.0 V)
Open Loop Voltage Gain (VO = 2.0 V to 4.0 V)
Unity Gain Bandwidth (TJ = 25°C)
Power Supply Rejection Ratio (VCC = 12 V to 25 V)
Output Current
Sink (VO = 1.1 V, VFB = 2.7 V)
Source (VO = 5.0 V, VFB = 2.3 V)
Output Voltage Swing
High State (RL = 15 k to ground, VFB = 2.3 V)
Low State (RL = 15 k to Vref, VFB = 2.7 V)
(UC284XB, UC384XB)
(UC384XBV)
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 4 & 5)
(UC284XB, UC384XB)
(UC384XBV)
Maximum Current Sense Input Threshold (Note 4)
(UC284XB, UC384XB)
(UC384XBV)
Power Supply Rejection Ratio
VCC = 12 V to 25 V, Note 4
Input Bias Current
Propagation Delay (Current Sense Input to Output)
OUTPUT SECTION
Output Voltage
Low State (ISink = 20 mA)
(ISink = 200 mA)
High State
V
VOL
–
–
–
13
–
12
–
–
–
0.1
1.6
–
13.5
–
13.4
0.1
50
50
0.4
2.2
–
–
–
–
1.1
150
150
–
–
–
13
12.9
12
–
–
–
0.1
1.6
1.6
13.5
13.5
13.4
0.1
50
50
0.4
2.2
2.3
–
–
–
1.1
150
150
V
ns
ns
AV
2.85
–
Vth
0.9
–
PSRR
IIB
tPLH(In/Out)
–
–
–
1.0
–
70
– 2.0
150
1.1
–
–
–10
300
0.9
0.85
–
–
–
1.0
1.0
70
– 2.0
150
1.1
1.1
–
–10
300
dB
µA
ns
3.0
–
3.15
–
2.85
2.85
3.0
3.0
3.15
3.25
V
V/V
VFB
IIB
AVOL
BW
PSRR
ISink
ISource
VOH
VOL
2.45
–
65
0.7
60
2.0
– 0.5
5.0
–
–
2.5
– 0.1
90
1.0
70
12
–1.0
6.2
0.8
–
2.55
–1.0
–
–
–
–
–
–
1.1
–
2.42
–
65
0.7
60
2.0
– 0.5
5.0
–
–
2.5
– 0.1
90
1.0
70
12
–1.0
6.2
0.8
0.8
2.58
– 2.0
–
–
–
–
–
V
–
1.1
1.2
V
µA
dB
MHz
dB
mA
Symbol
Min
Typ
Max
UC384XB, XBV
Min
Typ
Max
Unit
(UC284XB, UC384XB)
(UC384XBV)
(ISource = 20 mA) (UC284XB, UC384XB)
(UC384XBV)
(ISource = 200 mA)
VOH
Output Voltage with UVLO Activated
VCC = 6.0 V, ISink = 1.0 mA
Output Voltage Rise Time (CL = 1.0 nF, TJ = 25°C)
Output Voltage Fall Time (CL = 1.0 nF, TJ = 25°C)
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold (VCC)
UCX842B, BV
UCX843B, BV
Minimum Operating Voltage After Turn–On (VCC)
UCX842B, BV
UCX843B, BV
VOL(UVLO)
tr
tf
Vth
15
7.8
VCC(min)
9.0
7.0
10
7.6
11
8.2
8.5
7.0
10
7.6
11.5
8.2
16
8.4
17
9.0
14.5
7.8
16
8.4
17.5
9.0
V
V
NOTES:
2. Adjust VCC above the Startup threshold before setting to 15 V.
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
Tlow = 0°C for UC3842B, UC3843B
Thigh = +70°C for UC3842B, UC3843B
Tlow =
–25°C for UC2842B, UC2843B
Thigh =
+85°C for UC2842B, UC2843B
Tlow =
–40°C for UC3842BV, UC3843BV
Thigh =
+105°C for UC3842BV, UC3843BV
4. This parameter is measured at the latch trip point with VFB = 0 V.
∆V
Output Compensation
5. Comparator gain is defined as: AV
∆V
Current Sense Input
MOTOROLA ANALOG IC DEVICE DATA
3
UC3842B, 43B UC2842B, 43B
ELECTRICAL CHARACTERISTICS
(VCC = 15 V [Note 2], RT = 10 k, CT = 3.3 nF, for typical values TA = 25°C, for min/max values TA
is the operating ambient temperature range that applies [Note 3], unless otherwise noted.)
UC284XB
Characteristics
PWM SECTION
Duty Cycle
Maximum (UC284XB, UC384XB)
Maximum
(UC384XBV)
Minimum
TOTAL DEVICE
Power Supply Current
Startup (VCC = 6.5 V for UCX843B,
Startup
(VCC 14 V for UCX842B, BV)
Operating (Note 2)
Power Supply Zener Voltage (ICC = 25 mA)
ICC + IC
–
–
VZ
30
0.3
12
36
0.5
17
–
–
–
30
0.3
12
36
0.5
17
–
V
mA
%
DC(max)
DC(min)
94
–
–
96
–
–
–
–
0
94
93
–
96
96
–
–
–
0
Symbol
Min
Typ
Max
Min
UC384XB, BV
Typ
Max
Unit
NOTES:
2. Adjust VCC above the Startup threshold before setting to 15 V.
3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
Tlow = 0°C for UC3842B, UC3843B
Thigh = +70°C for UC3842B, UC3843B
Tlow =
–25°C for UC2842B, UC2843B
Thigh =
+85°C for UC2842B, UC2843B
Tlow =
–40°C for UC3842BV, UC3843BV
Thigh =
+105°C for UC3842BV, UC3843BV
Figure 1. Timing Resistor
versus Oscillator Frequency
80
% DT, PERCENT OUTPUT DEADTIME
50
R T, TIMING RESISTOR (k
Ω
)
20
8.0
5.0
2.0
0.8
10 k
VCC = 15 V
TA = 25°C
20 k
50 k
100 k
200 k
500 k
fOSC, OSCILLATOR FREQUENCY (kHz)
1.0 M
100
Figure 2. Output Deadtime
versus Oscillator Frequency
1. CT = 10 nF
50 2. CT = 5.0 nF
3. CT = 2.0 nF
4. CT = 1.0 nF
20 5. CT = 500 pF
6. CT = 200 pF
10 7. CT = 100 pF
5.0
2.0
1.0
10 k
20 k
4
3
2
1
5
6
7
VCC = 15 V
TA = 25°C
50 k
100 k
200 k
500 k
fOSC, OSCILLATOR FREQUENCY (kHz)
1.0 M
Figure 3. Oscillator Discharge Current
versus Temperature
9.0
I dischg , DISCHARGE CURRENT (mA)
VCC = 15 V
VOSC = 2.0 V
8.5
D max , MAXIMUM OUTPUT DUTY CYCLE (%)
100
90
80
70
60
50
40
0.8
Figure 4. Maximum Output Duty Cycle
versus Timing Resistor
Idischg = 7.5 mA
8.0
Idischg = 8.8 mA
7.5
VCC = 15 V
CT = 3.3 nF
TA = 25°C
5.0 6.0 7.0 8.0
7.0
– 55
– 25
0
25
50
75
TA, AMBIENT TEMPERATURE (°C)
100
125
1.0
2.0
3.0
4.0
RT, TIMING RESISTOR (kΩ)
4
MOTOROLA ANALOG IC DEVICE DATA
UC3842B, 43B UC2842B, 43B
Figure 5. Error Amp Small Signal
Transient Response
2.55 V
VCC = 15 V
AV = –1.0
TA = 25°C
20 mV/DIV
3.0 V
Figure 6. Error Amp Large Signal
Transient Response
VCC = 15 V
AV = –1.0
TA = 25°C
2.50 V
2.5 V
2.45 V
0.5
µs/DIV
2.0 V
1.0
µs/DIV
Figure 7. Error Amp Open Loop Gain and
Phase versus Frequency
A VOL , OPEN LOOP VOLTAGE GAIN (dB)
100
80
Gain
60
40
Phase
20
0
120
150
100
1.0 k
10 k
100 k
1.0 M
180
10 M
VCC = 15 V
VO = 2.0 V to 4.0 V
RL = 100 K
TA = 25°C
Vth, CURRENT SENSE INPUT THRESHOLD (V)
0
30
60
90
φ
EXCESS PHASE (DEGREES)
,
1.2
Figure 8. Current Sense Input Threshold
versus Error Amp Output Voltage
VCC = 15 V
1.0
0.8
0.6
TA = 125°C
0.4
0.2
0
TA = –55°C
TA = 25°C
– 20
10
0
f, FREQUENCY (Hz)
2.0
4.0
6.0
VO, ERROR AMP OUTPUT VOLTAGE (V)
8.0
I SC , REFERENCE SHORT CIRCUIT CURRENT (mA)
Figure 9. Reference Voltage Change
versus Source Current
∆
Vref , REFERENCE VOLTAGE CHANGE (mV)
0
Figure 10. Reference Short Circuit Current
versus Temperature
110
VCC = 15 V
– 4.0
– 8.0
–12
–16
VCC = 15 V
RL
≤
0.1
Ω
90
TA = –55°C
TA = 125°C
70
– 20
– 24
TA = 25°C
60
0
20
40
80
100
120
50
– 55
– 25
0
25
50
75
100
125
Iref, REFERENCE SOURCE CURRENT (mA)
TA, AMBIENT TEMPERATURE (°C)
MOTOROLA ANALOG IC DEVICE DATA
5
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