MICREL MIC38C43-1BM, MIC38C43-1BN, MIC38C43BM, MIC38C43BMM, MIC38C42BN Datasheet

MIC38C42/3/4/5 Micrel

MIC38C42/3/4/5

BiCMOS Current-Mode PWM Controllers

General Description

The MIC38C4x are fixed frequency, high performance, cur­rent-mode PWM controllers. Micrel’s BiCMOS devices are
pin compatible with 384x bipolar devices but feature several
improvements.

Undervoltage lockout circuitry allows the ’42 and ’44 versions
to start up at 14.5V and operate down to 9V, and the ’43 and
’45 versions start at 8.4V with operation down to 7.6V. All
versions operate up to 20V.

When compared to bipolar 384x devices operating from a
15V supply, start-up current has been reduced to 50µA
typical and operating current has been reduced to 4.0 mA
typical. Decreased output rise and fall times drive larger
MOSFETs, and rail-to-rail output capability increases effi­ciency, especially at lower supply voltages. The MIC38C4x
also features a trimmed oscillator discharge current and
bandgap reference.

MIC38C4x denotes 8-pin plastic DIP, SOIC, and MM8™
packages. MIC38C4x-1 denotes 14-pin plastic DIP and
SOIC packages. 8-pin devices feature small size, while 14­pin devices separate the analog and power connections for
improved performance and power dissipation.

Features

• Fast 40ns output rise and 30ns output fall times

• –40°C to +85°C temperature range
meets UC284x specifications

• High-performance, low-power BiCMOS Process

• Ultralow start-up current (50µA typical)

• Low operating current (4mA typical)

• CMOS outputs with rail-to-rail swing

• ≥ 500kHz current-mode operation

• Trimmed 5V bandgap reference

• Pin-for-pin compatible with UC3842/3843/3844/3845(A)

• Trimmed oscillator discharge current

• UVLO with hysteresis

• Low cross-conduction currents

Applications

• Current-mode, off-line, switched-mode power supplies

• Current-mode, dc-to-dc converters.

• Step-down “buck” regulators

• Step-up “boost” regulators

• Flyback, isolated regulators

• Forward converters

• Synchronous FET converters

For fast rise and fall times and higher output drive, refer to the
MIC38HC4x.

Functional Diagram

VDD

7 (12)

VREF

8 (14)

RT/CT

4 (7)

FB

2 (3)

2.5V

( ) pins are on MIC38C4x-1 (14-lead) versions only
* MIC38C4x (8-lead) versions only

†

MIC38C42, MIC38C43 (96% max. duty cycle) versions only

‡

MIC38C44, MIC38C45 (50% max. duty cycle) versions only

MM8 is a trademark of Micrel, Inc.

35V

COMP

1 (1)

5V

Reference

Oscillator

2R

R

GND*(AGND)

5 (9)

ISNS

3 (5)

UVLO

*

TQ

S

Q

R

*

(VD)

†

‡

(11)

OUT

6 (10)

(PGND)

(8)

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

August 2000 1 MIC38C42/3/4/5

MIC38C42/3/4/5 Micrel

Ordering Information

Part Number Temperature Range Package

MIC38C42BN –40°C to +85°C 8-pin Plastic DIP

MIC38C43BN –40°C to +85°C 8-pin Plastic DIP

MIC38C44BN –40°C to +85°C 8-pin Plastic DIP

MIC38C45BN –40°C to +85°C 8-pin Plastic DIP

MIC38C42-1BN –40°C to +85°C 14-pin Plastic DIP

MIC38C43-1BN –40°C to +85°C 14-pin Plastic DIP

MIC38C44-1BN –40°C to +85°C 14-pin Plastic DIP

MIC38C45-1BN –40°C to +85°C 14-pin Plastic DIP

MIC38C42BM –40°C to +85°C 8-pin SOIC

MIC38C43BM –40°C to +85°C 8-pin SOIC

MIC38C44BM –40°C to +85°C 8-pin SOIC

MIC38C45BM –40°C to +85°C 8-pin SOIC

MIC38C42BMM –40°C to +85°C 8-pin MM8™

MIC38C43BMM –40°C to +85°C 8-pin MM8™

MIC38C44BMM –40°C to +85°C 8-pin MM8™

MIC38C45BMM –40°C to +85°C 8-pin MM8™

MIC38C42-1BM –40°C to +85°C 14-pin SOIC

MIC38C43-1BM –40°C to +85°C 14-pin SOIC

MIC38C44-1BM –40°C to +85°C 14-pin SOIC

MIC38C45-1BM –40°C to +85°C 14-pin SOIC

Refer to the Part Number Cross Reference for a listings of Micrel devices equivalent to UC284x and UC384x devices.

Selection Guide

UVLO Thresholds

Startup 8.4V Startup 14.5V

Duty Cycle Minimum Operating 7.6V Minimum Operating 9V

0% to 96% MIC38C43 MIC38C42

0% to 50% MIC38C45 MIC38C44

MIC38C42/3/4/5 2 August 2000

MIC38C42/3/4/5 Micrel

2NC NC13

3FB VDD12

4NC VD11

5ISNS OUT10

6NC AGND9

7RT/CT PGND8

1COMP VREF14

MIC38C4x-1

Pin Configuration

MIC38C4x

COMP

FB

ISNS

RT/CT

1

2

3

4

8

7

6

5

VREF

VDD

OUT

GND

8-Pin DIP (N)

8-Lead SOIC (M)

14-Pin DIP (-1BN)

14-Lead SOIC (-1BM)

8-Lead MM8™ (MM)

Pin Description

Pin Number Pin Number Pin Name Pin Function

N, M, MM -1BN, -1BM

1 1 COMP Compensation: Connect external compensation network to modify the error

amplifier output.

2 NC Not internally connected.

2 3 FB Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output

voltage.

4 NC Not internally connected.

3 5 ISNS Current Sense (Input): Current sense comparator input. Connect to current

sensing resistor or current transformer.

6 NC Not internally connected.

4 7 RT/CT Timing Resistor/Timing Capacitor: Connect external RC network to select

switching frequency.

5 GND Ground: Combined analog and power ground.

8 PGND Power Ground: N-channel driver transistor ground.

9 AGND Analog Ground: Controller circuitry ground.

6 10 OUT Power Output: Totem-pole output.

11 VD Power Supply (Input): P-channel driver transistor supply input. Return to

power ground (PGND).

7 12 VDD Analog Supply (Input): Controller circuitry supply input. Return to analog

ground (AGND).

13 NC Not internally connected.

8 14 VREF 5V Reference (Output): Connect external RC network.

August 2000 3 MIC38C42/3/4/5

MIC38C42/3/4/5 Micrel

Absolute Maximum Ratings

Zener Current (VDD) ...................................................30mA

Operation at

special precautions (Note 6).

Supply Voltage (V

DD

Switch Supply Voltage (VD) ..........................................20V

Current Sense Voltage (V
Feedback Voltage (V
Output Current, 38C42/3/4/5 (I
Storage Temperature (T

≥18V may require

), Note 6 .......................................20V

) ..................... –0.3V to 5.5V

ISNS

) ................................ –0.3V to 5.5V

FB

) ............................. 0.5A

OUT

) ....................... –65°C to +150°C

A

Operating Ratings

Junction Temperature (TJ) ........................................ 150°C

Package Thermal Resistance

8-Pin Plastic DIP (θ

8-Pin MM8™ (θJA) ............................................. 250°C/W

8-Pin SOIC (θJA) ...............................................170°C/W

14-Pin Plastic DIP (θJA) ....................................... 90°C/W

14-Pin SOIC (θJA) .............................................145°C/W

) ....................................... 125°C/W

JA

Electrical Characteristics

VDD = 15V, Note 4; RT = 11.0k; CT = 3.3nF; –40°C ≤ TA ≤ 85°C; unless noted

Parameter Test Conditions Min Typ Max Units

Reference Section

Output Voltage TA = 25°C, IO = 1mA 4.90 5.00 5.10 V

Line Regulation 12V ≤ VDD ≤ 18V, IO = 5µA, Note 6 220mV

Load Regulation 1 ≤ IO ≤ 20mA 1 25 mV

Temp. Stability Note 1 0.2 mV/°C

Total Output Variation Line, Load, Temp., Note 1 4.82 5.18 V

Output Noise Voltage 10Hz ≤ f ≤ 10kHz, TA = 25°C, Note 1 50 µV

Long Term Stability TA = 125°C, 1000 hrs., Note 1 525mV

Output Short Circuit –30 –80 –180 mA

Oscillator Section

Initial Accuracy TA = 25°C, Note 5 49 52 55 kHz

Voltage Stability 12 ≤ VDD ≤ 18V, Note 6 0.2 1.0 %

Temp. Stability T

Clock Ramp TA = 25°C, V

Reset Current TA = T

Amplitude V

Error Amp Section

Input Voltage V

Input Bias Current VFB = 5.0V –0.1 –2 µA

A

VOL

Unity Gain Bandwidth Note 1 0.7 1.0 MHz

≤ TA ≤ T

MIN

to T

MIN

peak to peak 1.9 Vp-p

RT/CT

= 2.5V 2.42 2.50 2.58 V

COMP

2 ≤ VO ≤ 4V 65 90 dB

, Note 1 0.04 %/°C

MAX

= 2V 7.7 8.4 9.0 mA

RT/CT

MAX

7.2 8.4 9.5 mA

PSRR 12 ≤ VDD ≤ 18V 60 dB

Output Sink Current VFB = 2.7V, V

Output Source Current VFB = 2.3V, V

V

High VFB = 2.3V, RL = 15k to ground 5 6.8 V

OUT

V

Low VFB = 2.7V, RL = 15k to V

OUT

= 1.1V 2 14 mA

COMP

= 5V –0.5 –1mA

COMP

REF

0.1 1.1 V

MIC38C42/3/4/5 4 August 2000