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PDF MIC38C44A Data sheet ( Hoja de datos )
| Número de pieza | MIC38C44A | |
| Descripción | BiCMOS Current-Mode PWM Controllers | |
| Fabricantes | Micrel Semiconductor | |
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MIC38C42A/43A/44A/45A
Micrel, Inc.
MIC38C42A/43A/44A/45A
BiCMOS Current-Mode PWM Controllers
General Description
Features
The MIC38C4xA are fixed frequency, high performance,
• Fast 40ns output rise and 30ns output fall times
current-mode PWM controllers. Micrel’s BiCMOS devices
• –40°C to +85°C temperature range
are pin compatible with 384x bipolar devices but feature
meets UC284x specifications
several improvements.
• High-performance, low-power BiCMOS Process
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 50 µA
typical and operating current has been reduced to 4.0mA
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 MIC38C4xA
• Ultralow start-up current (100µA 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
• Trimmed oscillator discharge current
• UVLO with hysteresis
• Low cross-conduction currents
Applications
also features a trimmed oscillator discharge current and
bandgap reference.
• Current-mode, off-line, switched-mode power supplies
• Current-mode, dc-to-dc converters.
The MIC38C4xA family is available in 8-pin SOIC and MSOP- • Step-down “buck” regulators
8 (MM8) package options
• Step-up “boost” regulators
• Flyback, isolated regulators
For fast rise and fall times and higher output drive, refer to the
MIC38HC4x.
• Forward converters
• Synchronous FET converters
Functional Diagram
VDD
7
VREF
8
RT/CT
4
FB
2
2.5V
5V
Reference
Oscillator
2R
R
UVLO
†
TQ
‡
S
R
Q
OUT
6
COMP
1
GND ISNS
53
† MIC38C42A, MIC38C43A (96% max. duty cycle) versions only
‡ MIC38C44A, MIC38C45A (50% max. duty cycle) versions only
MM8 is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
http://www.Datasheet4U.com
April 2005
1 M9999-042205
1 page  
MIC38C42A/43A/44A/45A
Micrel, Inc.
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
MIC38C42A/4A
13.5 14.5 15.5
V
MIC38C43A/5A
7.8 8.4 9.0
V
Minimum Operating Voltage
MIC38C42A/4A
8 9 10 V
MIC38C43A/5A
7.0 7.6 8.2
V
Pulse Width Modulator
Maximum Duty Cycle
MIC38C42A/3A
94 96
%
MIC38C44A/5A
46 50
%
Minimum Duty Cycle
0%
Total Standby Current
Start-Up Current
VDD = 13V for MIC38C42A/44A
VDD = 7.5V for MIC38C43A/45A
100 230
µA
Operating Supply Current
VFB = VISNS = 0V
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:
4.0 6.0 mA
A=
∆ VPIN1 ;
VTH IS(NS )
0
≤≤VTH (ISNS )
0.8V
Note 4: Adjust V above the start threshold before setting at 15V.
DD
Note 5: Output frequency equals oscillator frequency for the MIC38C42 and MIC38C43. Output frequency for the MIC38C44A, and
MIC38C45A equals one half the oscillator frequency.
Note 6: Specification for packaged product only.
April 2005
5 M9999-042205
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet MIC38C44A.PDF ] | |
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