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PDF MIC38C42BM Data sheet ( Hoja de datos )
| Número de pieza | MIC38C42BM | |
| Descripción | BiCMOS Current-Mode PWM Controllers | |
| Fabricantes | Micrel Semiconductor | |
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MIC38C42/3/4/5
Micrel
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description
The MIC38C4x are fixed frequency, high performance, cur-
rent-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 effi-
ciency, 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 14-
pin 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
35V
5V
Reference
Oscillator
2R
R
UVLO
*
†
TQ
‡
S
R
Q
(VD)
(11)
OUT
6 (10)
(PGND)
(8)
*
COMP GND*(AGND) ISNS
1 (1)
5 (9)
3 (5)
( ) 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.
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 MIC38C42/3/4/5
1 page  
MIC38C42/3/4/5
Micrel
Parameter
Test Conditions
Min Typ Max Units
Current Sense
Gain
Notes 2, 3
2.85 3.0 3.15 V/V
MaximumThreshold
PSRR
Input Bias Current
VCOMP = 5V, Note 2
12 ≤ VDD ≤ 18V, Note 2
0.9 1 1.1
70
–0.1 –2
V
dB
µA
Delay to Output
120 250
ns
Output
RDS(ON) High
RDS(ON) Low
Rise Time
Fall Time
Undervoltage Lockout
ISOURCE = 200mA
ISINK = 200mA
TA = 25°C, CL = 1nF
TA = 25°C, CL = 1nF
20 Ω
11 Ω
40 80 ns
30 60 ns
Start Threshold
MIC38C42/4
13.5 14.5 15.5
V
MIC38C43/5
7.8 8.4 9.0
V
Minimum Operating Voltage
MIC38C42/4
8 9 10 V
MIC38C43/5
7.0 7.6 8.2
V
Pulse Width Modulator
Maximum Duty Cycle
MIC38C42/3
94 96
%
MIC38C44/5
46 50
%
Minimum Duty Cycle
0%
Total Standby Current
Start-Up Current
VDD = 13V for MIC38C42/44
VDD = 7.5V for MIC38C43/45
50 200 µA
Operating Supply Current
VFB = VISNS = 0V
4.0 6.0 mA
Zener Voltage (VDD)
IDD = 25mA, Note 6
Note 1: These parameters, although guaranteed, are not 100% tested in production.
Note 2: Parameter measured at trip point of latch with V = 0.
EA
Note 3: Gain defined as:
30 37
V
A=
∆ VPIN1 ;
VTH (ISNS )
0
≤
VTH (ISNS )
≤
0.8V
Note 4: Adjust VDD above the start threshold before setting at 15V.
Note 5: Output frequency equals oscillator frequency for the MIC38C42 and MIC38C43. Output frequency for the MIC38C44, and
MIC38C45 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.
August 2000
5 MIC38C42/3/4/5
5 Page 
MIC38C42/3/4/5
Micrel
August 2000
11 MIC38C42/3/4/5
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MIC38C42BM.PDF ] | |
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