B3842_B3843_B3844_B3848.pdf

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Bay Linear
Inspire the Linear Power
Current Mode PWM Controller
B3842/43/44/45A&A1
Description
Features
• 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
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.
Applications
• Switching Power Supply
• Monitor
Pin Connection
Ordering Information
Devices Package Temp.
B384X(Z)M SO-8 0 °C to 70 °C
B384X(Z)P 8-DIP 0 °C to 70 °C
Z=A ON Semi Z=A1 Fairchild & Samsung
8-Pin Surface Mount
COMP
1
8
REF
NC
2
7
VCC
ISENSE
3
6
OUTPUT
RT/CT
4
5
GND
Top View
Bay Linear, Inc 2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556 www.baylinear.com
8-Pin Surface Mount
COMP
1
8
REF
NC
2
7
VCC
3
6
OUTPUT
ISENSE
RT/CT
4
5
GND
Top View
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B384X
Absolute Maximum Rating
Parameter
Symbol
Value
Unit
Supply Voltage
V CC
30
V
Output Current
I O
±1
A
Analog Input (pin 2,3)
V (ANA)
-0.3 to 6.3
V
Error Amp Output Sink Current
I SINK (E.A)
10
mA
Power Dissipation
P D
1
W
Storage Temperature Range
T
-65 to 150
°C
Lead Temperature (Soldering 10 Sec.)
T L
260
°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
TYP MAX UNIT
REFERENCE SECTIO N
Reference Voltage
V REF
T J = 25 °C. I REF = 1mA
4.90
5.00
5.10
V
Line Regulation
REG (line) 12V≤V CC ≤25V
-
6
20
mA
Load Regulation
REG
(LOAD)
1mA≤I REF ≤20mA
T= 25 °C
-
6
25
Short Circuit Output
Current
I SC
T= 25 °C
-
-100
-180
mA
OSCILLATOR SECTION
Oscillator Frequency
f
T= 25 °C
47
52
57
KHz
Frequency Change with
Voltage
∆f/∆V CC 12V≤V CC ≤25V
-
0.05
1
%
Oscillator Amplitude
V OSC
-
1.6
-
V P-P
ERROR AMPLIFIER SEC TION
Input Bias Current
I BIAS
-
-0.1
-2 µA
Input Voltage
V I(E>A)
V 1 =2.5V
2.42
2.50
2.58
V
Open Loop Voltage Gain
G VO
2V≤V O ≤4V
65
90
-
dB
Power Supply Rejection
Ratio
PSRR
12V≤V CC ≤25V
60
70
-
dB
Output Sink Current
I SINK
V 2 =2.7V, V 1 =1.1V
2
7
-
mA
Output Source Current
I SOURCE V 2 =2.3, V 1 =5V
-0.6
-1.0
-
mA
High Output Voltage
V OH
V 2 =2.3, R L = 15Ω to GND
5
6
-
V
Low Output Voltage
V OL
V 2 =2.7, R L = 15Ω to pin 8
-
0.8
1.1
V
OUTPUT SECTION
Low Output Voltage
V OL
I SINK = 20mA
-
0.08
1.4
0.4
2.2
V
I SINK = 200mA
High Output Voltage
V OH
S ource = 20mA
13
12
13.5
13.0
-
-
V
S ource = 200mA
Rise Time
t R
T J = 25 °C, C L =1nF (note3)
-
45
150
ns
Fall Time
t F
T J = 25 °C, C L =1nF (note3)
-
35
150
ns
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
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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
TYP MAX UNIT
CURRENT SENSE SECTI ON
Gain
G V
(Note 1 & 2)
2.85
3
3.15
V/V
Maximum input Signal
V I(MAX) V 1 = 5V (Note 1)
0.9
1
1.1
V
Power Supply Rejection
Ratio
PSRR
12V≤V CC ≤25V
70
-
dB
Input Bias Current
I BIAS
-3
-10 µA
UNDER-VOLTAGE LOC KOUT SECTION
B3842/B3844
V TH(ST)
14.5
16
17.5
V
B3843/B3845
7.8
8.4
9
Min-Operating Voltage
(after Turn On)
V OPR(MIN)
B3842/B3844
8.5
10
11.5
V
B3843/B3845
7.0
7.6
8.2
PWM SECTION
Max Duty Cycle
D(MAX)
B3842/B3843
95
47
97
48
100
50
%
B3844/B3845
Min Duty Cycle
D (MIN)
-
-
0
%
TOTAL STANDBY CURR ENT
Start-Up Current
I ST
B3842A/43A/44A/45A
-
0.17
0.3
mA
B3842A1/43A1/44A1/45A1
0.45
1
Operating Supply Current
I CC(OPR) V 3 =V 2 =ON
-
14
17
mA
Zener Voltage
V Z
I CC
30
38
-
V
Block Diagram
Bay Linear, Inc 2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556 www.baylinear.com
Start Threshold
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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
383658255.013.png
B384X
Bay Linear, Inc 2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556 www.baylinear.com
383658255.014.png

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