MIC38C42AYMM [MICREL]
BiCMOS Current-Mode PWM Controllers; BiCMOS电流模式PWM控制器
| 型号： | MIC38C42AYMM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | BiCMOS Current-Mode PWM Controllers |
| 文件： | 总9页 (文件大小：123K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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,
current-mode PWM controllers. Micrel’s BiCMOS devices
are pin compatible with 384x bipolar devices but feature
several improvements.
• 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 (100µA typical)
• Low operating current (4mA typical)
• CMOS outputs with rail-to-rail swing
• ≥ 500kHz current-mode operation
• Trimmed 5V bandgap reference
Undervoltagelockoutcircuitryallowsthe’42and’44versions
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 4.0mA
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
also features a trimmed oscillator discharge current and
bandgap reference.
• Pin-for-pin compatible with UC3842/3843/3844/3845
• 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
TheMIC38C4xAfamilyisavailablein8-pinSOICandMSOP-
8 (MM8) package options
• Flyback, isolated regulators
• Forward converters
For fast rise and fall times and higher output drive, refer to the
MIC38HC4x.
• Synchronous FET converters
Functional Diagram
VDD
7
5V
UVLO
VREF
Reference
8
†
Oscillator
RT/CT
FB
OUT
4
2
6
T
Q
Q
‡
2R
R
S
R
2.5V
COMP
GND ISNS
MIC38C42A, MIC381C43A (96% max. 5duty cyc3le) 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
M9999-042205
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MIC38C42A/43A/44A/45A
Micrel, Inc.
Ordering Information
Part Number
Temperature
Range
Standard
Pb-Free
Package
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin MM8™
8-pin MM8™
8-pin MM8™
8-pin MM8™
MIC38C42ABM
MIC38C43ABM
MIC38C44ABM
MIC38C45ABM
MIC38C42ABMM
MIC38C43ABMM
MIC38C44ABMM
MIC38C45ABMM
MIC38C42AYM
MIC38C43AYM
MIC38C44AYM
MIC38C45AYM
MIC38C42AYMM
MIC38C43AYMM
MIC38C44AYMM
MIC38C45AYMM
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
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
0% to 96%
0% to 50%
Minimum Operating 7.6V Minimum Operating 9V
MIC38C43A
MIC38C45A
MIC38C42A
MIC38C44A
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MIC38C42A/43A/44A/45A
Micrel, Inc.
Pin Configuration
MIC38C4xA
COMP
FB
1
2
3
4
8
7
6
5
VREF
VDD
OUT
GND
ISNS
RT/CT
8-Lead SOIC (M)
8-Lead MM8™ (MM)
Pin Description
Pin Number
Pin Name
Pin Function
1
COMP
Compensation: Connect external compensation network to modify the error
amplifier output.
2
3
4
FB
Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output
voltage.
ISNS
RT/CT
Current Sense (Input): Current sense comparator input. Connect to current
sensing resistor or current transformer.
Timing Resistor/Timing Capacitor: Connect external RC network to select
switching frequency.
5
6
7
GND
OUT
VDD
Ground: Combined analog and power ground.
Power Output: Totem-pole output.
Analog Supply (Input): Controller circuitry supply input. Return to analog
ground (AGND).
8
VREF
5V Reference (Output): Connect external RC network.
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Micrel, Inc.
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (V ) ....................................................20V
Junction Temperature (T ) ........................................ 150°C
DD
J
Switch Supply Voltage (V ) ..........................................20V
Package Thermal Resistance
D
ISNS
8-Pin MM8™ (θ ).............................................250°C/W
Current Sense Voltage (V
) ..................... –0.3V to 5.5V
JA
8-Pin SOIC (θ ) ...............................................170°C/W
JA
Feedback Voltage (V )................................ –0.3V to 5.5V
FB
Output Current (I
) ...................................................0.5A
OUT
Storage Temperature (T ) ....................... –65°C to +150°C
A
Electrical Characteristics(Note 6)
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
Line Regulation
Load Regulation
Temp. Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Initial Accuracy
TA = 25°C, IO = 1mA
12V ≤ VDD ≤ 18V, IO = 5µA
1 ≤ IO ≤ 20mA
4.90
5.00
2
1
5.10
20
25
V
mV
mV
mV/°C
V
µV
mV
mA
Note 1
0.2
Line, Load, Temp., Note 1
10Hz ≤ f ≤ 10kHz, TA = 25°C, Note 1
TA = 125°C, 1000 hrs., Note 1
4.82
5.18
50
5
–80
25
–180
–30
47
TA = 25°C, Note 5
12 ≤ VDD ≤ 18V
53
0.2
0.04
8.4
59
1.0
kHz
%
%/°C
mA
Voltage Stability
Temp. Stability
T
MIN ≤ TA ≤ TMAX, Note 1
Clock Ramp
TA = 25°C, VRT/CT = 2V, Note 1
7.7
9.0
Reset Current
Amplitude
VRT/CT peak to peak
1.9
Vp-p
Error Amp Section
Input Voltage
Input Bias Current
AVOL
Unity Gain Bandwidth
PSRR
Output Sink Current
Output Source Current
VOUT High
VCOMP = 2.5V
VFB = 5.0V
2 ≤ VO ≤ 4V
Note 1
2.4
2.50
–0.1
90
2.58
–2
V
µA
dB
MHz
dB
mA
mA
V
65
0.7
60
2
–0.3
5
1.0
12 ≤ VDD ≤ 18V
VFB = 2.7V, VCOMP = 1.1V
VFB = 2.3V, VCOMP = 5V
VFB = 2.3V, RL = 15k to ground
VFB = 2.7V, RL = 15k to VREF
14
–1
6.8
0.1
VOUT Low
1.1
V
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Micrel, Inc.
Parameter
Test Conditions
Min
Typ
Max
Units
Current Sense
Gain
MaximumThreshold
PSRR
Input Bias Current
Delay to Output
Output
Notes 2, 3
VCOMP = 5V, Note 2
12 ≤ VDD ≤ 18V, Note 2
2.85
0.9
3.0
1
70
–0.1
120
3.15
1.1
V/V
V
dB
µA
ns
–2
250
RDS(ON) High
RDS(ON) Low
ISOURCE = 200mA
ISINK = 200mA
20
11
Ω
Ω
Rise Time
Fall Time
TA = 25°C, CL = 1nF
TA = 25°C, CL = 1nF
40
30
80
60
ns
ns
Undervoltage Lockout
Start Threshold
MIC38C42A/4A
MIC38C43A/5A
MIC38C42A/4A
MIC38C43A/5A
13.5
7.8
8
14.5
8.4
9
15.5
9.0
10
V
V
V
V
Minimum Operating Voltage
7.0
7.6
8.2
Pulse Width Modulator
Maximum Duty Cycle
MIC38C42A/3A
MIC38C44A/5A
94
46
96
50
%
%
%
Minimum Duty Cycle
Total Standby Current
Start-Up Current
0
VDD = 13V for MIC38C42A/44A
VDD = 7.5V for MIC38C43A/45A
VFB = VISNS = 0V
100
4.0
230
6.0
µA
Operating Supply Current
mA
Note 1: These parameters, although guaranteed, are not 100% tested in production.
Note 2: Parameter measured at trip point of latch with VEA = 0.
Note 3: Gain defined as:
∆ VPIN1
A =
; 0 ≤ VTH (ISNS) ≤ 0.8V
VTH (ISNS
)
Note 4: Adjust V above the start threshold before setting at 15V.
Note 5: Output frDeDquency 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.
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Micrel, Inc.
Typical Characteristics
Oscillator Frequency
Configuration
MIC38C42/43 Output Dead Time
vs. Oscillator Frequency
Oscillator Discharge
Current vs. Temperature
100
100
9.0
8.8
8.6
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
200pF
VDD = 15V
470pF
1nF
4.7nF
10nF
10
10
200pF
470pF
1nF
18nF
1.8nF
4.7nF
10nF
VDD = 15V
V
OSC = 2V
VDD = 15V
1
1
4
5
5
4
5
6
-60 -30
0
30 60 90 120 150
1x10
1x10
5x10
1x10
1x10
FREQUENCY (Hz)
1x10
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (Hz)
Current Sense Amplifier
vs. Error Amplifier Output
Short-Circuit Reference
MIC38C4x
Current vs. Temperature
Output Waveform
1.2
1.0
0.8
0.6
0.4
0.2
0.0
120
100
80
60
40
20
0
25
20
15
10
5
125°C
25°C
0
-5
-50°C
VD = 15V
L = 1nF
VDD = 15V
-10
-15
C
0
2
4
6
8
-60 -30
0
30 60 90 120 150
0.0
0.2
0.4
0.6
0.8
1.0
ERROR AMPLIFIER OUTPUT (V)
TEMPERATURE (°C)
TIME (µs)
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Micrel, Inc.
mended.
Application Information
Familiarity with 384x converter designs is assumed.
MIC38C4x Advantages
Whendesigninghigh-frequencyconverters, avoidcapacitive
and inductive coupling of the switching waveform into high-
impedancecircuitrysuchastheerroramplifier,oscillator,and
current sense amplifier. Avoid long printed-circuit traces and
component leads. Locate oscillator and compensation cir-
cuitry near the IC. Use high frequency decoupling capacitors
Start-up Current
Start-up current has been reduced to an ultra-low 50µA
(typical) permitting higher-valued, lower-wattage, start-up
resistors (powers controller during power supply start-up).
Thereducedresistorwattagereducescostandprintedcircuit
space.
on V
, and if necessary, on V . Return high di/dt currents
REF
DD
directly to their source and use large area ground planes.
Buck Converter
Operating Current
Refer to figure 1. When at least 26V is applied to the input,
C5ischargedthroughR2untilthevoltageV isgreaterthan
Operating current has been reduced to 4mA compared to
11mA for a typical bipolar controller. The controller runs
DD
14.5V (the undervoltage lockout value of the MIC38C42).
Output switching begins when Q1 is turned on by the gate
drive transformer T1, charging the output filter capacitor C3
cooler and the V
hold-up capacitance required during
DD
start-up may be reduced.
through L1. D5 supplies a regulated +12V to V once the
DD
Output Driver
circuit is running.
Complementary internal P- and N-channel MOSFETs pro-
ducerail-to-railoutputvoltagesforbetterperformancedriving
external power MOSFETs. The driver transistor’s low on-
resistance and high peak current capability can drive gate
capacitances of greater than 1000pF. The value of output
capacitance which can be driven is determined only by the
rise/fall time requirements. Within the restrictions of output
capacity and controller power dissipation, maximum switch-
ing frequency can approach 500kHz.
Current sense transformer CT1 provides current feedback to
ISNS for current-mode operation and cycle-by-cycle current
limiting. This is more efficient than a high-power sense
resistor and provides the required ground-referenced level
shift.
When Q1 turns off, current flow continues from ground
through D1 and L1 until Q1 is turned on again.
The 100V Schottky diode D1 reduces the forward voltage
drop in the main current path, resulting in higher efficiency
than could be accomplished using an ultra-fast-recovery
diode. R1 and C2 suppress parasitic oscillations from D1.
Design Precautions
When operating near 20V, circuit transients can easily ex-
ceedthe20Vabsolutemaximumrating,permanentlydamag-
ing the controller’s CMOS construction. To reduce tran-
sients,usea0.1µFlow-ESRcapacitortonexttothecontroller’s
Using a high-value inductance for L1 and a low-ESR capaci-
tor for C3 permits small capacitance with minimum output
ripple. This inductance value also improves circuit efficiency
by reducing the flux swing in L1.
supply V (or V for ‘-1’ versions) and ground connections.
DD
D
Film type capacitors, such as Wima MKS2, are recom-
VIN
VOUT
Q1
12V, 2A
IRF820
26V to 40V
CT1
L1 48µH
R2
R1
31DQ10
10
68k
D4
D1
1/2W
1N765B
C3
3.3µF
C4
0.1µF
C2
1000pF
C5
0.1µF*
4.7Ω
MKS2
4.7µF
D2
M17Z105
1/4W
0.1µF
6.8k
0.22µF
MIC38C42A
100k
1
8
7
6
5
COMP VREF
D3
D5
1N4001
2
3
4
MBR030
FB
VDD
6.19k
1%
T1
ISNS OUT
RT/CT GND
C8
0.1µF
R4
18
1.62k
1%
R5
*Locate near MIC38C42 supply pins
C7
0.1µF
16k
200pF
Figure 1. 500kHz, 25W, Buck Converter
April 2005
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M9999-042205
MIC38C42A/43A/44A/45A
Micrel, Inc.
Magnetic components are carefully chosen for minimal loss
at 500kHz. CT1 and T1 are wound on Magnetics, Inc. P-type
material toroids. L1 is wound on a Siemens N49 EFD core.
Test
Conditions
Results
0.5%
0.6%
90%
100mV
Symbol
CT1
T1
Custom Coil1
4923
4924
ETS2
Line Regulation VIN = 26V to 80V, IO = 2A
Load Regulation VIN = 48V, IO = 0.2A to 2A
Efficiency
ETS 92420
ETS 92419
ETS 92421
VIN = 48V, IO = 2A
VIN = 48V, IO = 2A (20MHz BW)
L1
4925
1. Custom Coils, Alcester, SD tel: (605) 934-2460
Output Ripple
2. Energy Transformation Systems, Inc. tel: (415) 324-4949.
Synchronous Buck Converter
Refer to figure 2. This MIC38C43 synchronous buck con-
verter uses an MIC5022 half-bridge driver to alternately drive
the PWM switch MOSFET (driven by GATEH, or high-side
output) and a MOSFET which functions as a synchronous
rectifier (driven by the GATEL, or low-side output).
The on-state voltage drop of the low-side MOSFET is lower
than the forward voltage drop of an equivalent Schottky
rectifier. This lower voltage drop results in higher efficiency.
A sense resistor (5mΩ) is connected to the driver’s high-side
current sense inputs to provide overcurrent protection. Refer
to the MIC5020, MIC5021, and MIC5022 data sheets for
more information.
Thelow-sideMOSFETturnsonwhenthehigh-sideMOSFET
is off, allowing current to return from ground. Current flows
through the low-side MOSFET in the source to drain direc-
tion.
+12V
SMP60N06-14
5mΩ
35µH
0.1µF
MIC5022
VDD GATEH
10k
0.15µF
VOUT
0.1µF
5V, 8A
NC
NC
FLT
EN
IN
VB
GATEL
SH+
MIC38C43A
COMP VREF
4.7nF
6.8k
300k
1000µF
470µF
25V
4.3k
Low ESR
FB
VDD
VOUT
GND
47k
NC
CT
SH–
ISNS
RT/CT
0.1µF*
MKS2
SL+
2200
pF
GND
SL–
3.3k 10k
*Locate near the MIC38C43 supply pins.
Figure 2. 100kHz, Synchronous Buck Converter
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April 2005
MIC38C42A/43A/44A/45A
Micrel, Inc.
Package Information
0.026 (0.65)
MAX)
PIN 1
0.157 (3.99)
0.150 (3.81)
DIMENSIONS:
INCHES (MM)
0.020 (0.51)
0.013 (0.33)
0.050 (1.27)
TYP
45°
0.0098 (0.249)
0.010 (0.25)
0.007 (0.18)
0.0040 (0.102)
0°–8°
0.197 (5.0)
0.189 (4.8)
0.050 (1.27)
0.016 (0.40)
SEATING
0.064 (1.63)
0.045 (1.14)
PLANE
0.244 (6.20)
0.228 (5.79)
8-Pin SOP (M)
0.122 (3.10)
0.199 (5.05)
DIMENSIONS:
INCH (MM)
0.112 (2.84)
0.187 (4.74)
0.120 (3.05)
0.116 (2.95)
0.036 (0.90)
0.032 (0.81)
0.043 (1.09)
0.038 (0.97)
0.012 (0.30) R
0.007 (0.18)
0.005 (0.13)
0.008 (0.20)
0.004 (0.10)
5° MAX
0° MIN
0.012 (0.03)
0.0256 (0.65) TYP
0.012 (0.03) R
0.039 (0.99)
0.035 (0.89)
0.021 (0.53)
8-Pin MSOP (MM)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2002 Micrel Incorporated
April 2005
9
M9999-042205
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