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UC3843B Datasheet

(UC3842B / UC3843B) HIGH PERFORMANCE CURRENT MODE CONTROLLERS


UC3843B Datasheet Preview


UC3842B, UC3843B,
UC2842B, UC2843B,
NCV3843BV
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 w8w.w5.DVataS(hoeent4)U.aconmd
7.6 V (off).
Trimmed Oscillator for Precise Frequency Control
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
VCC 7(12)
Vref
8(14)
RT/CT
4(7)
Voltage
Feedback
Input
2(3)
Output
Compensation
1(1)
R
5.0V
Reference
VCC
Undervoltage
Lockout
R
Vref
Undervoltage
Lockout
Oscillator
+
-
Error
Amplifier
Latching
PWM
Gnd 5(9)
Pin numbers in parenthesis are for the D suffix SO-14 package.
Figure 1. Simplified Block Diagram
VC
7(11)
Output
6(10)
Power
Ground
5(8)
Current
Sense
3(5) Input
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8
1
8
1
PDIP–8
N SUFFIX
CASE 626
SO–8
D1 SUFFIX
CASE 751
14
1
SO–14
D SUFFIX
CASE 751A
PIN CONNECTIONS
Compensation 1
Voltage Feedback 2
Current Sense 3
RT/CT 4
8 Vref
7 VCC
6 Output
5 Gnd
(Top View)
Compensation 1
NC 2
Voltage Feedback 3
NC 4
Current Sense 5
NC 6
RT/CT 7
14 Vref
13 NC
12 VCC
11 VC
10 Output
9 Gnd
8 Power Ground
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 16 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking
section on page 17 of this data sheet.
© Semiconductor Components Industries, LLC, 2001
December, 2001 – Rev. 3
1
Publication Order Number:
UC3842B/D
Page 1

UC3842B, UC3843B, UC2842B, UC2843B, NCV3843BV
MAXIMUM RATINGS
Rating
Bias and Driver Voltages (Zero Series Impedance, see also Total Device spec)
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, NCV3843BV
Storage Temperature Range
Symbol
VCC, VC
(ICC + IZ)
IO
W
Vin
IO
Value
30
30
1.0
5.0
– 0.3 to + 5.5
10
PD
RθJA
PD
RθJA
PD
RθJA
TJ
TA
Tstg
862
145
702
178
1.25
100
+150
0 to + 70
– 25 to + 85
–40 to +105
– 65 to +150
Unit
V
mA
A
µJ
V
mA
mW
°C/W
mW
°C/W
W
°C/W
°C
°C
°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
UC384XB, XBV
Characteristics
Symbol Min Typ Max Min Typ Max Unit
REFERENCE SECTION
Reference Output Voltage (IO = 1.0 mA, TJ = 25°C)
Vref 4.95 5.0 5.05 4.9 5.0 5.1 V
Line Regulation (VCC = 12 V to 25 V)
Regline
2.0 20
2.0 20
mV
Load Regulation (IO = 1.0 mA to 20 mA)
Temperature Stability
Regload
3.0 25
3.0 25
mV
TS
– 0.2 –
– 0.2 – mV/°C
Total Output Variation over Line, Load, and Temperature
Vref 4.9 – 5.1 4.82 – 5.18 V
Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C)
Long Term Stability (TA = 125°C for 1000 Hours)
Vn
– 50 –
– 50 –
µV
S
– 5.0 –
– 5.0 –
mV
Output Short Circuit Current
ISC – 30 – 85 –180 – 30 – 85 –180 mA
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)
fOSC
kHz
49 52 55 49 52 55
48 – 56 48 – 56
225 250 275 225 250 275
fOSC/V
0.2 1.0
0.2 1.0
%
Frequency Change with Temperature, TA = Tlow to Thigh
fOSC/T
1.0
– 0.5 –
%
Oscillator Voltage Swing (Peak–to–Peak)
VOSC
– 1.6 –
– 1.6 –
V
Discharge Current (VOSC = 2.0 V)
TJ = 25°C
TA = Tlow to Thigh (UC284XB, UC384XB)
TA = Tlow to Thigh (UC384XBV)
Idischg
7.8 8.3 8.8 7.8 8.3 8.8
7.5 – 8.8 7.6 – 8.8
– – – 7.2 – 8.8
mA
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; –25°C for UC2842B, UC2843B; –40°C for UC3842BV, UC3843BV
Thigh = +70°C for UC3842B, UC3843B; +85°C for UC2842B, UC2843B; +105°C for UC3842BV, UC3843BV
NCV3843BV: Tlow = –40°C, Thigh = +105°C. Guaranteed by design. NCV prefix is for automotive and other applications requiring site and
change control.
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2
Page 2

UC3842B, UC3843B, UC2842B, UC2843B, NCV3843BV
ELECTRICAL CHARACTERISTICS (VCC = 15 V [Note 4], 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 5], unless otherwise noted.)
UC284XB
UC384XB, XBV
Characteristics
Symbol Min Typ Max Min Typ Max Unit
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)
VFB
IIB
AVOL
BW
PSRR
ISink
ISource
VOH
VOL
2.45 2.5 2.55 2.42 2.5 2.58 V
– – 0.1 –1.0 – – 0.1 – 2.0 µA
65 90 – 65 90 – dB
0.7 1.0 – 0.7 1.0 – MHz
60 70 – 60 70 – dB
mA
2.0 12 – 2.0 12 –
– 0.5 –1.0 – – 0.5 –1.0 –
5.0 6.2 – 5.0 6.2 –
V
– 0.8 1.1 – 0.8 1.1
– – – – 0.8 1.2
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 6 & 7)
(UC284XB, UC384XB)
(UC384XBV)
AV V/V
2.85 3.0 3.15 2.85 3.0 3.15
– – – 2.85 3.0 3.25
Maximum Current Sense Input Threshold (Note 6)
(UC284XB, UC384XB)
(UC384XBV)
Vth V
0.9 1.0 1.1 0.9 1.0 1.1
– – – 0.85 1.0 1.1
Power Supply Rejection Ratio (VCC = 12 V to 25 V, Note 6)
Input Bias Current
Propagation Delay (Current Sense Input to Output)
OUTPUT SECTION
Output Voltage
Low State (ISink = 20 mA)
(ISink = 200 mA)
(UC284XB, UC384XB)
(UC384XBV)
High State (ISource = 20 mA) (UC284XB, UC384XB)
(UC384XBV)
(ISource = 200 mA)
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
PSRR
IIB
tPLH(In/Out)
VOL
VOH
VOL(UVLO)
tr
tf
Vth
13
12
15
7.8
70
– 2.0
150
–10
300
0.1 0.4
1.6 2.2
––
13.5 –
––
13.4 –
0.1 1.1
50 150
50 150
16 17
8.4 9.0
– 70 –
– – 2.0 –10
– 150 300
– 0.1
– 1.6
– 1.6
13 13.5
12.9 13.5
12 13.4
– 0.1
– 50
– 50
0.4
2.2
2.3
1.1
150
150
14.5 16 17.5
7.8 8.4 9.0
dB
µA
ns
V
V
ns
ns
V
Minimum Operating Voltage After Turn–On (VCC)
UCX842B, BV
UCX843B, BV
VCC(min)
V
9.0 10 11 8.5 10 11.5
7.0 7.6 8.2 7.0 7.6 8.2
4. Adjust VCC above the Startup threshold before setting to 15 V.
5. 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; –25°C for UC2842B, UC2843B; –40°C for UC3842BV, UC3843BV
Thigh = +70°C for UC3842B, UC3843B; +85°C for UC2842B, UC2843B; +105°C for UC3842BV, UC3843BV
NCV3843BV: Tlow = –40°C, Thigh = +125°C. Guaranteed by design. NCV prefix is for automotive and other applications requiring site and
change control.
6. This parameter is measured at the latch trip point with VFB = 0 V.
7. Comparator gain is defined as: AV
V Output Compensation
V Current Sense Input
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3
Page 3
Part Number UC3843B
Manufactur ON Semiconductor
Description (UC3842B / UC3843B) HIGH PERFORMANCE CURRENT MODE CONTROLLERS
Total Page 20 Pages
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