MIC38C42YMMTR [MICREL]
0.5A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, PDSO8, LEAD FREE, MSOP-8;型号: | MIC38C42YMMTR |
厂家: | MICREL SEMICONDUCTOR |
描述: | 0.5A SWITCHING CONTROLLER, 500kHz SWITCHING FREQ-MAX, PDSO8, LEAD FREE, MSOP-8 控制器 |
文件: | 总11页 (文件大小:346K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description
Features
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.
• 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
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
15Vsupply,start-upcurrenthasbeenreducedto50µAtypical
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, espe-
cially at lower supply voltages. The MIC38C4x also features
a trimmed oscillator discharge current and bandgap refer-
ence.
• 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
The MIC38C4x denotes 8-pin plastic DIP, SOIC, and MSOP
packages. MIC384Cx-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 perfomance and power dissipation.
• Synchronous FET converters
For fast rise and fall times and higher output drive, refer to
the MIC38HC4x.
Functional Diagram
*
VDD
7 (12)
35V
5V
Reference
(VD)
UVLO
VREF
(11)
8 (14)
†
‡
Oscillator
RT/CT
OUT
4 (7)
6 (10)
T
Q
Q
FB
2R
R
2 (3)
(PGND)
(8)
S
R
2.5V
*
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
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
M9999-091107
September 2007
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MIC38C42/3/4/5
Micrel, Inc.
Ordering Information
Part Number*
Temperature Range
Package
Standard
Pb-Free
MIC38C42BN
MIC38C43BN
MIC38C44BN
MIC38C45BN
MIC38C42-1BN
MIC38C43-1BN
MIC38C44-1BN
MIC38C45-1BN
MIC38C42BM
MIC38C43BM
MIC38C44BM
MIC38C45BM
MIC38C42BMM
MIC38C43BMM
MIC38C44BMM
MIC38C45BMM
MIC38C42-1BM
MIC38C43-1BM
MIC38C44-1BM
MIC38C45-1BM
MIC38C42YN
MIC38C43YN
MIC38C44YN
MIC38C45YN
Contact Factory
Contact Factory
MIC38C44-1YN
Contact Factory
MIC38C42YM
MIC38C43YM
MIC38C44YM
MIC38C45YM
MIC38C42YMM
MIC38C43YMM
MIC38C44YMM
MIC38C45YMM
MIC38C42-1YM
MIC38C43-1YM
MIC38C44-1YM
MIC38C45-1YM
-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
-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
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8-pin Plastic DIP
8-pin Plastic DIP
8-pin Plastic DIP
8-pin Plastic DIP
14-pin Plastic DIP
14-pin Plastic DIP
14-pin Plastic DIP
14-pin Plastic DIP
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin MSOP
8-pin MSOP
8-pin MSOP
8-pin MSOP
14-pin SOIC
14-pin SOIC
14-pin SOIC
14-pin SOIC
* Refer to the Part Number Cross Reference for a listing 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
MIC38C43
MIC38C45
MIC38C42
MIC38C44
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September 2007
MIC38C42/3/4/5
Micrel, Inc.
Pin Configuration
MIC38C4x-1
COMP
NC
1
2
3
4
5
6
14 VREF
13 NC
12 VDD
11 VD
FB
MIC38C4x
NC
COMP
FB
1
2
3
4
8
7
6
5
VREF
VDD
10 OUT
ISNS
NC
9
8
AGND
PGND
ISNS
RT/CT
OUT
RT/CT 7
GND
8-Pin DIP (N)
8-Pin SOIC (M)
8-Pin MSOP (MM)
14-Pin DIP (-1BN)
14-Pin SOIC (-1BM)
Pin Description
Pin Number
Pin Number
Pin Name
Pin Function
N, M, MM
-1BN, -1BM
1
2
3
1
COMP
Compensation: Connect external compensation network to modify the error
amplifier output.
2
3
NC
FB
Not internally connected.
Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output
voltage.
4
5
NC
Not internally connected.
ISNS
Current Sense (Input): Current sense comparator input. Connect to current
sensing resistor or current transformer.
6
7
NC
Not internally connected.
4
5
RT/CT
Timing Resistor/Timing Capacitor: Connect external RC network to select
switching frequency.
GND
PGND
AGND
OUT
Ground: Combined analog and power ground.
Power Ground: N-channel driver transistor ground.
Analog Ground: Controller circuitry ground.
Power Output: Totem-pole output.
8
9
6
7
8
10
11
VD
Power Supply (Input): P-channel driver transistor supply input. Return to
power ground (PGND).
12
VDD
Analog Supply (Input): Controller circuitry supply input. Return to analog
ground (AGND).
13
14
NC
Not internally connected.
VREF
5V Reference (Output): Connect external RC network.
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Absolute Maximum Ratings
Operating Ratings
Zener Current (V ) ................................................... 30mA
Junction Temperature (T )......................................... 150°C
DD
J
Operation at ≥18V may require
special precautions (Note 6).
Package Thermal Resistance
8-Pin Plastic DIP (θ ).......................................125°C/W
JA
8-Pin MSOP (θ )..............................................250°C/W
Supply Voltage (V ), Note 6........................................20V
JA
DD
8-Pin SOIC (θ )................................................170°C/W
JA
Switch Supply Voltage (V )...........................................20V
D
14-Pin Plastic DIP (θ ) ......................................90°C/W
JA
Current Sense Voltage (V
).......................–0.3V to 5.5V
ISNS
14-Pin SOIC (θ )..............................................145°C/W
JA
Feedback Voltage (V ) .................................–0.3V to 5.5V
FB
Output Current, 38C42/3/4/5 (I
) ............................. 0.5A
OUT
Storage Temperature (T )......................... –65°C to +150°C
A
Electrical Characteristics
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
TA = 25°C, IO = 1mA
4.90
5.00
2
5.10
20
V
mV
mV
mV/°C
V
Line Regulation
Load Regulation
Temp. Stability
12V ≤ VDD ≤ 18V, IO = 5µA, Note 6
1 ≤ IO ≤ 20mA
1
25
Note 1
0.2
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Initial Accuracy
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
µV
25
mV
mA
–30
49
–80
–180
TA = 25°C, Note 5
52
0.2
55
kHz
%
Voltage Stability
Temp. Stability
12 ≤ VDD ≤ 18V, Note 6
1.0
TMIN ≤ TA ≤ TMAX, Note 1
0.04
%/°C
Clock Ramp
TA = 25°C, VRT/CT = 2V
TA = TMIN to TMAX
7.7
7.2
8.4
8.4
9.0
9.5
mA
mA
Reset Current
Amplitude
VRT/CT peak to peak
1.9
Vp-p
Error Amp Section
Input Voltage
Input Bias Current
AVOL
VCOMP = 2.5V
FB = 5.0V
2.42
2.50
–0.1
90
2.58
–2
V
µA
dB
MHz
dB
mA
mA
V
V
2 ≤ VO ≤ 4V
Note 1
65
0.7
60
2
Unity Gain Bandwidth
PSRR
1.0
12 ≤ VDD ≤ 18V
Output Sink Current
Output Source Current
VOUT High
V
FB = 2.7V, VCOMP = 1.1V
FB = 2.3V, VCOMP = 5V
14
–1
V
–0.5
5
VFB = 2.3V, RL = 15k to ground
VFB = 2.7V, RL = 15k to VREF
6.8
0.1
VOUT Low
1.1
V
M9999-091107
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September 2007
MIC38C42/3/4/5
Parameter
Micrel, Inc.
Test Conditions
Min
Typ
Max
Units
Current Sense
Gain
Notes 2, 3
2.85
0.9
3.0
1
3.15
1.1
V/V
V
MaximumThreshold
PSRR
VCOMP = 5V, Note 2
12 ≤ VDD ≤ 18V, Note 2
70
dB
µA
ns
Input Bias Current
Delay to Output
Output
–0.1
120
–2
250
RDS(ON) High
RDS(ON) Low
ISOURCE = 200mA
ISINK = 200mA
20
11
Ω
Ω
Rise Time
TA = 25°C, CL = 1nF
TA = 25°C, CL = 1nF
40
30
80
60
ns
ns
Fall Time
Undervoltage Lockout
Start Threshold
MIC38C42/4
MIC38C43/5
MIC38C42/4
MIC38C43/5
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
MIC38C42/3
MIC38C44/5
94
46
96
50
%
%
%
Minimum Duty Cycle
Total Standby Current
Start-Up Current
0
VDD = 13V for MIC38C42/44
VDD = 7.5V for MIC38C43/45
50
200
6.0
µA
Operating Supply Current
V
FB = VISNS = 0V
4.0
37
mA
V
Zener Voltage (VDD
)
IDD = 25mA, Note 6
30
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
; 0 ≤ VTH (ISNS) ≤ 0.8V
A =
VTH (ISNS
)
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.
September 2007
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MIC38C42/3/4/5
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
1x105
1.8nF
4.7nF
10nF
VDD = 15V
VOSC = 2V
VDD = 15V
1
1
1x104
1x104
1x105
5x10
1x106
-60 -30
0
30 60 90 120 150
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (Hz)
FREQUENCY (Hz)
Short-Circuit Reference
Current vs. Temperature
MIC38C4x
Output Waveform
Current Sense Amplifier
vs. Error Amplifier Output
1.2
120
100
80
60
40
20
0
25
20
15
10
5
1.0
0.8
0.6
0.4
0.2
0
125°C
25°C
-50°C
0
-5
VD = 15V
CL = 1nF
VDD = 15V
-10
-15
0.0
0
2
4
6
8
-60 -30
0
30 60 90 120 150
0.2
0.4
0.6
0.8
1.0
ERROR AMPLIFIER OUTPUT (V)
TEMPERATURE (°C)
TIME (µs)
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September 2007
MIC38C42/3/4/5
Micrel, Inc.
Whendesigninghigh-frequencyconverters, avoidcapacitive
and inductive coupling of the switching waveform into high-
impedancecircuitrysuchastheerroramplifier, oscillator, and
current sense amplifier. Avoid long printed-circuit traces and
componentleads.Locateoscillatorandcompensationcircuitry
near the IC. Use high frequency decoupling capacitors on
Application Information
Familiarity with 384x converter designs is assumed.
The MIC38C4x has been designed to be compatible with
384xA series controllers.
MIC38C4x Advantages
V
, and if necessary, on V . Return high di/dt currents
REF
DD
Start-up Current
directly to their source and use large area ground planes.
Start-up current has been reduced to an ultra-low 50µA(typi-
cal)permittinghigher-valued,lower-wattage,start-upresistors
(powerscontrollerduringpowersupplystart-up). Thereduced
resistor wattage reduces cost and printed circuit space.
Buck Converter
Refer to figure 1. When at least 26V is applied to the input,
C5 is charged through R2 until the voltage V
is greater
DD
than14.5V(theundervoltagelockoutvalueoftheMIC38C42).
Output switching begins when Q1 is turned on by the gate
drive transformer T1, charging the output filter capacitor C3
Operating Current
Operating current has been reduced to 4mA compared to
11mA for a typical bipolar controller. The controller runs
through L1. D5 supplies a regulated +12V to V once the
DD
cooler and the V
hold-up capacitance required during
circuit is running.
DD
start-up may be reduced.
Current sense transformer CT1 provides current feedback to
ISNS for current-mode operation and cycle-by-cycle current
limiting. Thisismoreefficientthanahigh-powersenseresistor
and provides the required ground-referenced level shift.
Output Driver
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
capacityandcontrollerpowerdissipation,maximumswitching
frequency can approach 500kHz.
WhenQ1turnsoff,currentflowcontinuesfromgroundthrough
D1 and L1 until Q1 is turned on again.
The100VSchottkydiodeD1reducestheforwardvoltagedrop
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.
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.
Design Precautions
Whenoperatingnear20V,circuittransientscaneasilyexceed
the20Vabsolutemaximumrating,permanentlydamagingthe
controller’s CMOS construction. To reduce transients, use
a 0.1µF low-ESR capacitor to next to the controller’s supply
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.
V
(or V for ‘-1’ versions) and ground connections. Film
DD
D
type capacitors, such as Wima MKS2, are recommended.
VIN
26V to 40V
VOUT
12V, 2A
Q1
IRF820
CT1
L1 48µH
R1
R2
68k
31DQ10
10
D4
1N765B
D1
1/2W
C3
3.3µF
C4
0.1µF
C2
1000pF
C5
4.7µF
0.1µF*
4.7Ω
MKS2
D2
M17Z105
1/4W
0.1µF
6.8k
MIC38C42
100k
1
8
7
6
5
COMP V R E F
D3
MBR030
0.22µF
D5
1N4001
2
3
4
FB
VDD
6.19k
T1
1%
ISNS OUT
RT/CT GND
C8
0.1µF
R4
18
1.62k
1%
R5
16k
*Locate near MIC38C42 supply pins
C7
0.1µF
200pF
Figure 1. 500kHz, 25W, Buck Converter
September 2007
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M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
Test
Conditions
Results
0.5%
Symbol
CT1
T1
Custom Coil1
4923
ETS2
Line Regulation VIN = 26V to 80V, IO = 2A
Load Regulation VIN = 48V, IO = 0.2A to 2A
ETS 92420
ETS 92419
ETS 92421
0.6%
4924
Efficiency
VIN = 48V, IO = 2A
90%
L1
4925
1. Custom Coils, Alcester, SD tel: (605) 934-2460
2. Energy Transformation Systems, Inc. tel: (415) 324-4949.
Output Ripple
VIN = 48V, IO = 2A (20MHz BW)
100mV
Synchronous Buck Converter
Refertofigure2. ThisMIC38C43synchronousbuckconverter
uses an MIC5022 half-bridge driver to alternately drive the
PWMswitchMOSFET(drivenbyGATEH,orhigh-sideoutput)
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 recti
-
fier. 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.
The low-side MOSFET turns on when the high-side MOS-
FET is off, allowing current to return from ground. Current
flows through the low-side MOSFET in the source to drain
direction.
+12V
SMP60N06-14
5mΩ
35µH
0.1µF
MIC5022
10k
0.15µF
4.7nF
VOUT
5V, 8A
VDD GATEH
0.1µF
NC
NC
FLT
EN
IN
VB
GATEL
SH+
MIC38C43
COMP V R E F
FB VDD
6.8k
300k
4.3k
1000µF
Low ESR
470µF
25V
47k
NC
CT
SH–
ISNS VOUT
RT/CT GND
0.1µF*
MKS2
SL+
2200
pF
GND
SL–
3.3k 10k
*Locate near the MIC38C43 supply pins.
Figure 2. 100kHz, Synchronous Buck Converter
M9999-091107
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September 2007
MIC38C42/3/4/5
Micrel, Inc.
Package Information
PIN 1
DIMENSIONS:
INCH (MM)
0.380 (9.65)
0.370 (9.40)
0.255 (6.48)
0.245 (6.22)
0.135 (3.43)
0.125 (3.18)
0.300 (7.62)
0.013 (0.330)
0.010 (0.254)
0.380 (9.65)
0.320 (8.13)
0.018 (0.57)
0.100 (2.54)
0.130 (3.30)
0.0375 (0.952)
8-Pin Plastic DIP (N)
.770 (19.558) MAX
PIN 1
.235 (5.969)
.215 (5.461)
.060 (1.524)
.045 (1.143)
.310 (7.874)
.280 (7.112)
.160 MAX
(4.064)
.080 (1.524)
.015 (0.381)
.015 (0.381)
.008 (0.2032)
.160 (4.064)
.100 (2.540)
.110 (2.794)
.090 (2.296)
.023 (.5842)
.015 (.3810)
.400 (10.180)
.330 (8.362)
.060 (1.524)
.045 (1.143)
14-Pin Plastic DIP (N)
September 2007
9
M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
8-Pin SOIC (M)
8-Pin MSOP (MM)
M9999-091107
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September 2007
MIC38C42/3/4/5
Micrel, Inc.
14-Pin SOIC (M)
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.
© 2000 Micrel Incorporated
September 2007
11
M9999-091107
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