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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 15VIN the start-up current is reduced to 50A (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 50A (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.
-40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
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
VDD VD IOUT VDD VISENSE VFB PD T TL
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
VDD = 15V (Note 4), RT = 11k, CT = 3.3nF, TA= -40C to +85C, unless otherwise specified Parameter Symbol Conditions MIN TYP REFERENCE SECTION
Reference Voltage Line Regulation Load Regulation Short Circuit Output Current VREF REG (LINE) REG(LOAD) ISC TJ = 25 C. IREF = 1mA 12VVDD18V, IO = 5A 1mAIREF20mA T= 25 C T= 25 C 12VVCC25V 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 % VP-P A V dB dB mA mA V V V V ns ns
MAX
UNIT
OSCILLATOR SECTION Oscillator Frequency f Frequency Change with Voltage f/VCC Oscillator Amplitude VOSC ERROR AMPLIFIER SECTION Input Bias Current IBIAS Input Voltage VI(E>A) Open Loop Voltage Gain GVO Power Supply Rejection Ratio PSRR Output Sink Current ISINK Output Source Current ISOURCE High Output Voltage VOH Low Output Voltage VOL OUTPUT SECTION Low Output Voltage High Output Voltage Rise Time Fall Time VOL VOH tR tF
V1 =2.5V 2VVO4V 12VVCC25V V2 =2.7V, V1 =1.1V V2=2.3, V1=5V V2=2.3, RL= 15 to GND V2=2.7, RL= 15 to pin 8 ISINK = 20mA ISINK = 200mA Source = 20mA Source = 200mA TJ = 25 C, CL=1nF (note3) TJ = 25 C, CL=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
(VCC = 15V;RT = 10, CT = 3.3nF, TA=0 C to +70C, 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 A V V
CURRENT SENSE SECTION Gain GV (Note 1 & 2) Maximum input Signal VI(MAX) V1 = 5V (Note 1) Power Supply Rejection PSRR 12VVCC25V Ratio Input Bias Current IBIAS UNDER-VOLTAGE LOCKOUT SECTION B3842/B3844 Start Threshold VTH(ST) B3843/B3845 B3842/B3844 Min-Operating Voltage VOPR(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 IST ICC(OPR) VZ IST B3842A/43A/44A/45A B3842B/43B/44B/45B V3=V2=ON ICC 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
% % A mA V mA C/W C/W
PACKAGE THERMAL RESISTANCE 8-SOIC JA 8-PDip 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 VDD VREF
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 VREF 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 VCC 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 A, with a maximum limit of 120 A. Low start- up current allows high resistance, lowerwattage, start- up resistors to supply controller startup 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 ONresistance 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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