MIC38HC42 Micrel Semiconductor, MIC38HC42 Datasheet

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MIC38HC42

Manufacturer Part Number
MIC38HC42
Description
BiCMOS 1A Current-Mode PWM Controllers
Manufacturer
Micrel Semiconductor
Datasheet

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MIC38HC42/3/4/5
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 de-
vices. 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 effi-
ciency, 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.
Functional Diagram
August 2000
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
RT/CT
VREF
VDD
7 (12)
8 (14)
4 (7)
2 (3)
FB
( ) 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
2.5V
COMP
1 (1)
35V
GND*(AGND)
Reference
Oscillator
5
2R
5V
R
(9)
ISNS
3 (5)
1
UVLO
Features
• Fast 20ns output rise and 15ns output fall times
• –40°C to +85°C temperature range
• 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
BiCMOS 1A Current-Mode PWM Controllers
exceeds UC284x specifications
T
S
R
MIC38HC42/3/4/5
*
*
Q
Q
(VD)
(11)
OUT
6 (10)
(PGND)
(8)
MIC38HC42/3/4/5
Micrel

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MIC38HC42 Summary of contents

Page 1

... 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 ‡ Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com ...

Page 2

... MIC38HC45BM MIC38HC42-1BM MIC38HC43-1BM MIC38HC44-1BM MIC38HC45-1BM Selection Guide Duty Cycle 50% MIC38HC42/3/4/5 Temperature Range Package –40°C to +85°C 8-pin Plastic DIP –40°C to +85°C 8-pin Plastic DIP –40°C to +85°C 8-pin Plastic DIP –40°C to +85°C 8-pin Plastic DIP – ...

Page 3

... Analog Supply (Input): Controller circuitry supply input. Return to analog ground (AGND). NC Not internally connected. VREF 5V Reference (Output): Connect external RC network. 3 MIC38HC4x-1 COMP 1 14 VREF VDD ISNS 5 10 OUT AGND RT/ PGND 14-Pin DIP (-1BN) 14-Lead SOIC (-1BM) MIC38HC42/3/4/5 Micrel ...

Page 4

... Output Source Current High V OUT FB V Low V OUT FB MIC38HC42/3/4/5 Operating Junction Temperature (T Package Thermal Resistance 8-Pin Plastic DIP (θ 8-Pin MM8™ (θ 8-Pin SOIC (θ 14-Pin Plastic DIP (θ 14-Pin SOIC (θ Storage Temperature (T ) .............................. 1A ≤ 85°C; unless noted A = 25°C, I ...

Page 5

... DD Note 5: Output frequency equals oscillator frequency for the MIC38HC42 and MIC38HC43. Output frequency for the MIC38HC44, and MIC38HC45 equals one half the oscillator frequency. Note 6: On 8-pin version, 20V is maximum input on pin 7, as this is also the supply pin for the output stage. On 14-pin version, 40V is maximum for pin 12 and 20V maximum for pin 11 ...

Page 6

... OSCILLATOR FREQUENCY (Hz) Current Sense Amplifier vs. Error Amplifier Output 1.2 1.0 125°C 0.8 0.6 25°C 0.4 -50°C 0.2 0 ERROR AMPLIFIER OUTPUT (V) MIC38HC42/3/4/5 MIC38C/HC42/43 Output Dead Time vs. Oscillator Frequency 100 V = 15V DD 4.7nF 10 200pF 10nF 470pF 1nF 18nF 1x10 1x10 1x10 FREQUENCY (Hz) Short-Circuit Reference Current vs ...

Page 7

... Plastic DIP (N) 7 0.255 (6.48) 0.245 (6.22) 0.300 (7.62) 0.013 (0.330) 0.010 (0.254) .310 (7.874) .280 (7.112) .015 (0.381) .008 (0.2032) .400 (10.180) .330 (8.362) MIC38HC42/3/4/5 Micrel ...

Page 8

... This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. MIC38HC42/3/4/5 MAX) PIN 1 ...

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