Bay Linear
Inspire the Linear Power
Current Mode PWM Controller
Description
The Bay Linear B3842/43/44/45 are fixed frequency current-
mode PWM controller. These devices are designed for Off-
Line and DC-to-DC converter applications with minimum
external components. The B3842 family Feature a trimmed
oscillator for precise duty cycle control, a temperature
compensated reference, high gain error amplifier, current
sensing comparator, and a high current totempole output.
Ideally suited for driving a power N-Channel MOSFET’s. It is
low when is on off stage. Protection circuitry includes built in
under-voltage lockout and current limiting.
Major differences between members of these series are the
UVLO thresholds and maximum duty-cycle ranges. Typical
UVLO thresholds of 16V (on) and 10V (off) on the B3842 and
B3844 devices make them ideally suited to off-line
applications. These corresponding typical thresholds for the
B3842 and B3845 devcies are 8.4V (on) and 7.6V (off). The
B3842 and B3843 devcies can operate to duty cycles
approaching 100%. A duty-Cycle range of 0 to 50% is
obtained by the B3844 and B3845 by the addition of an
internal toggle flip-flop, which blanks the output off every
other clock cycle. It id available in 8 pin DIP and SOIC
packages.
B3842/43/44/45A&A1
•
•
•
•
•
Low Start-Up and Operating Current
Maximum Duty Cycle
Operating Frequency Up to 500KHz
Under voltage Lockout with Hysteresis
Available in 8 pin SOIC
Similar to industry Standard UC3842
Features
•
Applications
•
•
Switching Power Supply
Monitor
Pin Connection
Ordering Information
Devices
B384X(Z)M
B384X(Z)P
Z=A ON Semi
Package
Temp.
SO-8
0
°C
to 70
°C
8-DIP
0
°C
to 70
°C
Z=A1 Fairchild & Samsung
8-Pin Surface Mount
COMP
NC
1
2
3
4
8
7
6
5
REF
VCC
OUTPUT
GND
ISENSE
RT/CT
Top View
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B384X
Absolute Maximum Rating
Parameter
Supply Voltage
Output Current
Analog Input (pin 2,3)
Error Amp Output Sink Current
Power Dissipation
Storage Temperature Range
Lead Temperature (Soldering 10 Sec.)
Symbol
V
CC
I
O
V
(ANA)
I
SINK (E.A)
P
D
T
T
L
Value
30
±1
-0.3 to 6.3
10
1
-65 to 150
260
Unit
V
A
V
mA
W
°C
°C
Electrical Characteristics
(V
CC
= 15V;R
T
= 10Ω, C
T
= 3.3nF, T
A
=0
°C
to +70°C
, unless otherwise specified)
Parameter
Symbol Conditions
MIN
REFERENCE SECTION
Reference Voltage
Line Regulation
V
REF
REG
(line)
T
J
= 25
°C.
I
REF
= 1mA
12V≤V
CC
≤25V
1mA≤I
REF
≤20mA
T= 25
°C
T= 25
°C
4.90
-
TYP
5.00
6
MAX
5.10
20
UNIT
V
mA
Load Regulation
REG
(LOAD)
-
6
25
Short Circuit Output
Current
I
SC
-
-100
-180
mA
OSCILLATOR SECTION
Oscillator Frequency
f
Frequency Change with
∆f/∆V
CC
Voltage
Oscillator Amplitude
V
OSC
ERROR AMPLIFIER SECTION
Input Bias Current
I
BIAS
Input Voltage
V
I(E>A)
Open Loop Voltage Gain
G
VO
Power Supply Rejection
PSRR
Ratio
Output Sink Current
I
SINK
Output Source Current
I
SOURCE
High Output Voltage
V
OH
Low Output Voltage
V
OL
OUTPUT SECTION
Low Output Voltage
V
OL
High Output Voltage
Rise Time
Fall Time
V
OH
t
R
t
F
T= 25
°C
12V≤V
CC
≤25V
47
-
-
-
2.42
65
60
2
-0.6
5
-
-
13
12
-
-
52
0.05
1.6
-0.1
2.50
90
70
7
-1.0
6
0.8
0.08
1.4
13.5
13.0
45
35
57
1
-
-2
2.58
-
-
-
-
-
1.1
0.4
2.2
-
-
150
150
KHz
%
V
P-P
µA
V
dB
dB
mA
mA
V
V
V
V
ns
ns
V
1
=2.5V
2V≤V
O
≤4V
12V≤V
CC
≤25V
V
2
=2.7V, V
1
=1.1V
V
2
=2.3, V
1
=5V
V
2
=2.3, R
L
= 15Ω to GND
V
2
=2.7, R
L
= 15Ω to pin 8
I
SINK
= 20mA
I
SINK
= 200mA
S
ource
= 20mA
S
ource
= 200mA
T
J
= 25
°C,
C
L
=1nF (note3)
T
J
= 25
°C,
C
L
=1nF (note3)
Note:
Output Switch tests are performed under pulsed conditions to minimize power dissipation
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B384X
Electrical Characteristics
(V
CC
= 15V;R
T
= 10Ω, C
T
= 3.3nF, T
A
=0
°C
to +70°C
, unless otherwise specified)
Parameter
Symbol Conditions
MIN
CURRENT SENSE SECTION
Gain
G
V
(Note 1 & 2)
Maximum input Signal
V
I(MAX)
V
1
= 5V (Note 1)
Power Supply Rejection
PSRR
12V≤V
CC
≤25V
Ratio
Input Bias Current
I
BIAS
UNDER-VOLTAGE LOCKOUT SECTION
B3842/B3844
Start Threshold
V
TH(ST)
B3843/B3845
B3842/B3844
Min-Operating Voltage
V
OPR(MIN)
(after Turn On)
B3843/B3845
PWM SECTION
B3842/B3843
Max Duty Cycle
D(MAX)
B3844/B3845
Min Duty Cycle
D (MIN)
TOTAL STANDBY CURRENT
B3842A/43A/44A/45A
Start-Up Current
I
ST
B3842A1/43A1/44A1/45A1
Operating Supply Current
I
CC(OPR)
V
3
=V
2
=ON
Zener Voltage
V
Z
I
CC
2.85
0.9
TYP
3
1
70
-3
MAX
3.15
1.1
-
-10
17.5
9
11.5
8.2
100
50
0
0.3
1
17
-
UNIT
V/V
V
dB
µA
V
V
14.5
7.8
8.5
7.0
95
47
-
-
-
30
16
8.4
10
7.6
97
48
-
0.17
0.45
14
38
%
%
mA
mA
V
Block Diagram
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B384X
Figure 1: Error Amp Configuration
Figure 2: Under-Voltage Lockout
3842
3843
Figure 3: Current Sense Circuit
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
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