MICREL MIC38HC43BN, MIC38HC43BM, MIC38HC42BM, MIC38HC42BN, MIC38HC43-1BM Datasheet
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MIC38HC42/3/4/5 Micrel
MIC38HC42/3/4/5
BiCMOS 1A Current-Mode PWM Controllers
General Description
The MIC38HC4x family are fixed frequency current-mode
PWM controllers with 1A drive current capability. Micrel’s
BiCMOS devices are pin-compatible with 384x bipolar devices. Their high output drive, with fast rise and fall times,
combined with low startup current make it an ideal PWM
controller where high efficiency is required.
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 UC384x 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 MIC38HC4x
also features a trimmed oscillator discharge current and
bandgap reference.
MIC38HC4x-1 is available in 14-pin plastic DIP and SOIC
packages. 8-pin devices feature small size, while 14-pin
devices separate the analog and power connections for
improved performance and power dissipation.
Features
• Fast 20ns output rise and 15ns output fall times
• –40°C to +85°C temperature range
exceeds UC284x specifications
• High-performance, low-power BiCMOS Process
• Ultralow start-up current (50µA typical)
• Low operating current (4mA typical)
• High output drive (1A peak current, HC version)
• CMOS outputs with rail-to-rail swing
• Current-mode operation up to 500kHz
• 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
Functional Diagram
VDD
7 (12)
VREF
8 (14)
RT/CT
4 (7)
FB
2 (3)
2.5V
( ) pins are on MIC38HC4x-1 (14-lead) versions only
* MIC38HC4x (8-lead) versions only
†
MIC38HC42, MIC38HC43 (96% max. duty cycle) versions only
‡
MIC38HC44, MIC38HC45 (50% max. duty cycle) versions only
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 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
August 2000 1 MIC38HC42/3/4/5
MIC38HC42/3/4/5 Micrel
Ordering Information
Part Number Temperature Range Package
MIC38HC42BN –40°C to +85°C 8-pin Plastic DIP
MIC38HC43BN –40°C to +85°C 8-pin Plastic DIP
MIC38HC44BN –40°C to +85°C 8-pin Plastic DIP
MIC38HC45BN –40°C to +85°C 8-pin Plastic DIP
MIC38HC42-1BN –40°C to +85°C 14-pin Plastic DIP
MIC38HC43-1BN –40°C to +85°C 14-pin Plastic DIP
MIC38HC44-1BN –40°C to +85°C 14-pin Plastic DIP
MIC38HC45-1BN –40°C to +85°C 14-pin Plastic DIP
MIC38HC42BM –40°C to +85°C 8-pin SOIC
MIC38HC43BM –40°C to +85°C 8-pin SOIC
MIC38HC44BM –40°C to +85°C 8-pin SOIC
MIC38HC45BM –40°C to +85°C 8-pin SOIC
MIC38HC42-1BM –40°C to +85°C 14-pin SOIC
MIC38HC43-1BM –40°C to +85°C 14-pin SOIC
MIC38HC44-1BM –40°C to +85°C 14-pin SOIC
MIC38HC45-1BM –40°C to +85°C 14-pin SOIC
Selection Guide
UVLO Thresholds
Startup 8.4V Startup 14.5V
Duty Cycle Minimum Operating 7.6V Minimum Operating 9V
0% to 96% MIC38HC43 MIC38HC42
0% to 50% MIC38HC45 MIC38HC44
MIC38HC42/3/4/5 2 August 2000
MIC38HC42/3/4/5 Micrel
Pin Configuration
MIC38HC4x-1
1COMP VREF14
2NC NC13
3FB VDD12
COMP
FB
ISNS
RT/CT
MIC38HC4x
1
2
3
4
8-Pin DIP (N)
8-Lead SOIC (M)
8
7
6
5
VREF
VDD
OUT
GND
4NC VD11
5ISNS OUT10
6NC AGND9
7RT/CT PGND8
14-Pin DIP (-1BN)
14-Lead SOIC (-1BM)
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 MIC38HC42/3/4/5
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