BAYLI B3845P, B3845M, B3845AP, B3845AM, B3845A1P Datasheet

Bay Linear, Inc

2418 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

Current Mode PWM Controller

B3842/43/44/45A&A1

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

Description

The Bay Linear B3842/43/44/45 are fixed frequency current­mode PWM controller. These devices are designed for Off­Line 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.

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

Applications

• Switching Power Supply

• Monitor

2

1

3

4

8

7

6

5

8-Pin Surface Mount

Top View

COMP

ISENSE

RT/CT

GND

VCC

OUTPUT

REF

NC

2

1

3

4

8

7

6

5

8-Pin Surface Mount

Top View

COMP

ISENSE

RT/CT

GND

VCC

OUTPUT

REF

NC

Bay Linear

Inspire the Linear Power

Bay Linear, Inc

2418 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

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

(VCC = 15V;RT = 10Ω, CT = 3.3nF, TA=0 °C to +70°C, unless otherwise specified)

Parameter Symbol Conditions MIN TYP MAX UNIT

REFERENCE SECTION

Reference Voltage V

REF

TJ = 25 °C. I

REF

= 1mA

4.90 5.00 5.10 V

Line Regulation REG

(line)

12V≤VCC≤25V

- 6 20

Load Regulation REG

(LOAD)

1mA≤I

REF

≤20mA

T= 25 °C

- 6 25

mA

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≤VCC≤25V

- 0.05 1 %

Oscillator Amplitude V

OSC

- 1.6 - V

P-P

ERROR AMPLIFIER SECTION

Input Bias Current I

BIAS

- -0.1 -2

µA

Input Voltage V

I(E>A)

V1 =2.5V 2.42 2.50 2.58 V

Open Loop Voltage Gain G

VO

2V≤VO≤4V

65 90 - dB

Power Supply Rejection
Ratio

PSRR

12V≤V

CC

≤25V

60 70 - dB

Output Sink Current I

SINK

V2 =2.7V, V1 =1.1V 2 7 - mA

Output Source Current I

SOURCE V2

=2.3, V1=5V -0.6 -1.0 - mA

High Output Voltage V

OH

V2=2.3, RL= 15Ω to GND

5 6 - V

Low Output Voltage V

OL

V2=2.7, RL= 15Ω to pin 8

- 0.8 1.1 V

OUTPUT SECTION

I

SINK

= 20mA Low Output Voltage V

OL

I

SINK

= 200mA

- 0.08

1.4

0.4

2.2

V

S

ource

= 20mA High Output Voltage V

OH

S

ource

= 200mA

13
12

13.5

13.0

-

-

V

Rise Time t

R

TJ = 25 °C, CL=1nF (note3)

- 45 150 ns

Fall Time t

F

TJ = 25 °C, CL=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: [phone], Fax: [phone] www.baylinear.com

B384X

Electrical Characteristics

(VCC = 15V;RT = 10Ω, CT = 3.3nF, TA=0 °C to +70°C, unless otherwise specified)

Parameter Symbol Conditions MIN TYP MAX UNIT

CURRENT SENSE SECTION

Gain G

V

(Note 1 & 2) 2.85 3 3.15 V/V

Maximum input Signal V

I(MAX) V1

= 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 LOCKOUT SECTION

B3842/B3844 14.5 16 17.5

Start Threshold V

TH(ST)

B3843/B3845 7.8 8.4 9

V

B3842/B3844 8.5 10 11.5

Min-Operating Voltage
(after Turn On)

V

OPR(MIN)

B3843/B3845 7.0 7.6 8.2

V

PWM SECTION

B3842/B3843

Max Duty Cycle D(MAX)

B3844/B3845

95
47

97
48

100

50

%

Min Duty Cycle D (MIN) - - 0 %

TOTAL STANDBY CURRENT

B3842A/43A/44A/45A - 0.17 0.3

Start-Up Current I

ST

B3842A1/43A1/44A1/45A1 0.45 1

mA

Operating Supply Current I

CC(OPR) V3=V2

=ON - 14 17 mA

Zener Voltage V

Z

I

CC

30 38 - V

Block Diagram