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
UVLO Thresholds
Duty Cycle
Star-Up at 8.4V
Operating Min= 7.6V
Star-Up at 14.5V
Operating Min= 9.0V
0% to 96%
B38C43
B38C42
0% to 50%
B38C45
B38C44
Pin Descriptions
Pin No.#
Name
Function
1
COMP
Output of error amplifier & input to PWM comparator
2
FB
Inverting input of error amplifier
3
ISNS
Current sense comparator input. It is internally limited to 1V
4
RT/CT
Oscilator RC timing component connection. Resistor RT is connected to
VREF and capacitro CT is conencted to ground. Different values of RT
and CT determine the maximum duty cycle..
5
GND/PGND
Combined pwoer and analog ground
6
OUT
High-power, toten-pole driver output. OUT pin is activly held LOW
when VCC is below the UVLO threshold.
7
VDD
Suply votlage input
8
VREF
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
.
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
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.
B38C4X
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
