Bay Linear
Inspire the Linear Power
BiCMOS Current Mode PWM Controller
Description
The Bay Linear B38C42/43/44/45 are fixed frequency and
high performance current-mode PWM controller in BiCMOS.
They are pin compatible with all bipolar 384X’s controllers are
similar to the MIC38C4X family. These devices are designed
for DC-to-DC converter applications and feature a trimmed
oscillator discharge current and bandgap reference.
The benefit of the BiCMOS process provides significant
performance improvement compared to Bipolar 384X devices.
At 15V
IN
the start-up current is reduced to 50µA (typ.) from
0.17 mA with an operating current reduced to 4mA (typ.) from
14mA. Also, quicker output rise and fall times drive larger
MOSFET ‘s and rail-to-rail output capability improves
efficiency, especially lower supply voltages.
Major differences between members of these series are the
UVLO thresholds. Typical UVLO thresholds of 14.5V (on)
and 9V (off) for the B38C42 and B38C44 devices make them
ideally suited to off-line applications. The corresponding
typical thresholds for the B38C43 and B3845 devcies are 8.4V
(on) and 7.6V (off).
The B39C4X devices are available in 8 pin DIP and SOIC.
B38C42/43/44/45
Advance Information
Features
•
•
•
•
•
•
•
•
•
•
•
•
Low-Power BiCMOS Process
Ultra Low Start-Up Current of 50µA (typ.)
Very Lower Operating Current (4mA)
Current Mode Operation
≥
500KHz
CMOS outputs with Rail to Rail outputs
Under Voltage Lockout with Hysteresis
5V Trimmed Bandgap Reference
Trimmed Oscillator Discharged Current
Low Cross-Conduction Currents
Available in 8 pin SOIC and 8PDip
Similar to MIC38C42/43/44/45
Pin to Pin compatible with UC3842X Family
Applications
•
•
•
•
•
•
Switched and Current Mode Power Supplies
Off-line Power Supply
Step-Up (Buck), Step-Down (Boost) Regulator
Flyback, Isolated Regulators
Synchronous FET converters
Forward Converters
Pin Connection
Ordering Information
Devices
B38C42M
B38C42P
B38C43M
B38C43P
B38C44M
B38C44P
B38C45M
B38C45P
Package
SO-8
8-DIP
SO-8
8-DIP
SO-8
8-DIP
SO-8
8-DIP
Temp.
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8-SOIC and 8-PDip
COMP
FB
1
2
3
4
8
7
6
5
REF
VDD
OUTPUT
GND
ISENSE
RT/CT
Top
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B38C4X
Absolute Maximum Rating
Parameter
Supply Voltage
Switch Supply Voltage
Output Current
Zener Current
Current Sense Voltage
Feedback Voltage
Power Dissipation
Storage Temperature Range
Lead Temperature (Soldering 10 Sec.)
Symbol
V
DD
V
D
I
OUT
V
DD
V
ISENSE
V
FB
P
D
T
T
L
Value
20
20
1A
30
-0.3 to 5.5
-0.3 to 5.5
1
-65 to 150
300
Unit
V
V
A
mA
V
V
W
°C
°C
Electrical Characteristics
V
DD
= 15V (Note 4), R
T
= 11k, C
T
= 3.3nF, T
A
= -40
°C
to +85°C
, unless otherwise specified
Parameter
Symbol Conditions
MIN
TYP
REFERENCE SECTION
Reference Voltage
Line Regulation
Load Regulation
Short Circuit Output Current
V
REF
REG
(LINE)
REG
(LOAD)
I
SC
T
J
= 25
°C.
I
REF
= 1mA
12V≤V
DD
≤18V,
I
O
= 5µA
1mA≤I
REF
≤20mA
T= 25
°C
T= 25
°C
12V≤V
CC
≤25V
4.90
-
-
-30
47
-
-
-1
2.42
65
60
2
-0.5
5
-
-
13
12
-
-
5.00
2
1
-80
52
0.05
1.6
-0.1
2.50
90
70
6
-1.0
6
0.8
0.08
1.4
13.5
13.0
40
30
5.10
20
25
-180
57
1
2.3
1
2.58
-
-
-
-
-
1.1
0.4
2.2
-
-
70
50
V
mV
mA
KHz
%
V
P-P
µA
V
dB
dB
mA
mA
V
V
V
V
ns
ns
MAX
UNIT
OSCILLATOR SECTION
Oscillator Frequency
f
Frequency Change with Voltage
∆f/∆V
CC
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 Ratio
PSRR
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
High Output Voltage
Rise Time
Fall Time
V
OL
V
OH
t
R
t
F
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
B38C4X
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
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
120
120
17
-
0.3
170
125
UNIT
V/V
V
dB
µA
V
V
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/B3844
Max Duty Cycle
D(MAX)
B3843/B3845
Min Duty Cycle
D (MIN)
TOTAL STANDBY CURRENT
Start-Up Current
Operating Supply Current
Zener Voltage
Start-Up Current
I
ST
I
CC(OPR)
V
Z
I
ST
B3842A/43A/44A/45A
B3842B/43B/44B/45B
V
3
=V
2
=ON
I
CC
B3842A/43A/44A/45A
14.5
7.8
8.5
7.0
95
47
-
-
-
30
-
16
8.4
10
7.6
97
48
-
100
100
14
38
0.17
%
%
µA
mA
V
mA
°C/W
°C/W
PACKAGE THERMAL RESISTANCE
8-SOIC
θ
JA
8-PDip
θ
JA
14 Pin versions
This is
The base
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B38C4X
Startup & Operating Voltage Selection Guide
Duty Cycle
0% to 96%
0% to 50%
UVLO Thresholds
Star-Up at 8.4V
Star-Up at 14.5V
Operating Min= 7.6V
Operating Min= 9.0V
B38C43
B38C45
B38C42
B38C44
Pin Descriptions
Pin No.#
Name
1
2
3
4
5
6
7
8
COMP
FB
ISNS
RT/CT
GND/PGND
OUT
V
DD
V
REF
Function
Output of error amplifier & input to PWM comparator
Inverting input of error amplifier
Current sense comparator input. It is internally limited to 1V
Oscilator RC timing component connection. Resistor RT is connected to
V
REF
and capacitro CT is conencted to ground. Different values of RT
and CT determine the maximum duty cycle..
Combined pwoer and analog ground
High-power, toten-pole driver output. OUT pin is activly held LOW
when V
CC
is below the UVLO threshold.
Suply votlage input
5Volt reerence votlage output
Application Notes:
The Bay Linear B38C4X devices are compatible with
generic 384x PWM devices. The following discussion
highlights the differences and advantages of the Bay C
design.
Start- up Current
Bau Linear BiCMOS process allows for substantial
reduction in the start- up current. Typical start- up
current is 95 µ A, with a maximum limit of 120 µ A.
Low start- up current allows high resistance, lower-
wattage, start- up resistors to supply controller start-
up power
.
can exceed 1MHz.
The CMOS output stage “ break- before- make”
action is guaranteed by design and insures that no
cross- conduction current will flow. This
minimizes heat dissipation, increases efficiency
and enhances reliability.
Oscilator Operation
Two external components, RT and CT, set the
switching frequency.
With VCC = 14V, RT = 10k and CT = 3.3nF,
nominal switching frequency is 50kHz.
Output Driver
The B38C4x CMOS output stage drives external
power MOSFETs to the full supply voltage. Low ON-
resistance and high peak current drive combine to give
greater than 1000pF gate capacitance drive capability.
Rise and fall time requirements may dictate the
appropriate value of output capacitance. Within the
restrictions of output capacity and controller power
dissipation, switching frequencies
B38C4X
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
Advance Information-
These data sheets contain descriptions of products that are in development. The specifications are based on the engineering calculations,
computer simulations and/ or initial prototype evaluation.
Preliminary Information-
These data sheets contain minimum and maximum specifications that are based on the initial device characterizations. These limits are
subject to change upon the completion of the full characterization over the specified temperature and supply voltage ranges.
The application circuit examples are only to explain the representative applications of the devices and are not intended to guarantee any circuit
design or permit any industrial property right to other rights to execute. Bay Linear takes no responsibility for any problems related to any
industrial property right resulting from the use of the contents shown in the data book. Typical parameters can and do vary in different
applications. Customer’s technical experts must validate all operating parameters including “ Typical” for each customer application.
LIFE SUPPORT AND NUCLEAR POLICY
Bay Linear products are not authorized for and should not be used within life support systems which are intended for surgical
implants into the body to support or sustain life, in aircraft, space equipment, submarine, or nuclear facility applications without
the specific written consent of Bay Linear President.
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
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