MIC38C43-1BM [MICREL]
BiCMOS Current-Mode PWM Controllers; BiCMOS电流模式PWM控制器
| 型号： | MIC38C43-1BM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | BiCMOS Current-Mode PWM Controllers |
| 文件： | 总12页 (文件大小：101K) |
| 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
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.
• 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
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.
• 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
UVLO
VREF
(VD)
8 (14)
(11)
†
‡
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
‡
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
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MIC38C42/3/4/5
MIC38C42/3/4/5
Micrel
Ordering Information
Part Number
Temperature Range
Package
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
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
–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 SOIC
8-pin SOIC
8-pin SOIC
8-pin MM8™
8-pin MM8™
8-pin MM8™
8-pin MM8™
14-pin SOIC
14-pin SOIC
14-pin SOIC
14-pin SOIC
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
MIC38C43
MIC38C45
MIC38C42
MIC38C44
MIC38C42/3/4/5
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Pin Configuration
MIC38C4x-1
14 VREF
13 NC
COMP 1
NC
FB
2
3
4
5
6
7
12 VDD
11 VD
MIC38C4x
NC
COMP
FB
1
2
3
4
8
7
6
5
VREF
VDD
OUT
GND
10 OUT
9 AGND
8 PGND
ISNS
NC
ISNS
RT/CT
RT/CT
8-Pin DIP (N)
14-Pin DIP (-1BN)
8-Lead SOIC (M)
14-Lead SOIC (-1BM)
8-Lead MM8™ (MM)
Pin Description
Pin Number
N, M, MM
Pin Number
-1BN, -1BM
Pin Name
Pin Function
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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MIC38C42/3/4/5
MIC38C42/3/4/5
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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
Package Thermal Resistance
special precautions (Note 6).
8-Pin Plastic DIP (θ ).......................................125°C/W
JA
8-Pin MM8™ (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
–80
–180
TA = 25°C, Note 5
49
52
0.2
55
kHz
%
Voltage Stability
Temp. Stability
12 ≤ VDD ≤ 18V, Note 6
TMIN ≤ TA ≤ TMAX, Note 1
1.0
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
2.42
2.50
–0.1
90
2.58
V
µA
dB
MHz
dB
mA
mA
V
VFB = 5.0V
–2
2 ≤ VO ≤ 4V
65
0.7
60
2
Unity Gain Bandwidth
PSRR
Note 1
1.0
12 ≤ VDD ≤ 18V
Output Sink Current
Output Source Current
VOUT High
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
–0.5
5
6.8
0.1
VOUT Low
1.1
V
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MIC38C42/3/4/5
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Parameter
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
VFB = 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
VTH (ISNS
A =
; 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.
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MIC38C42/3/4/5
MIC38C42/3/4/5
Micrel
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
C
-15
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)
MIC38C42/3/4/5
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MIC38C42/3/4/5
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supply V (or V for ‘-1’ versions) and ground connections.
Film type capacitors, such as Wima MKS2, are recom-
mended.
Application Information
Familiarity with 384x converter designs is assumed.
DD
D
The MIC38C4x has been designed to be compatible with
384xA series controllers.
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
MIC38C4x Advantages
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
Refer to figure 1. When at least 26V is applied to the input,
Operating Current
C5ischargedthroughR2untilthevoltageV isgreaterthan
DD
Operating current has been reduced to 4mA compared to
11mA for a typical bipolar controller. The controller runs
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
start-up may be reduced.
hold-up capacitance required during
DD
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
VIN
26V to 40V
VOUT
12V, 2A
Q1
IRF820
CT1
L1 48µH
R1
R2
68k
31DQ10
D1
10
D4
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
MIC38C42
100k
1
8
7
6
5
COMP VREF
D3
0.22µF
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
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MIC38C42/3/4/5
MIC38C42/3/4/5
Micrel
ripple. This inductance value also improves circuit efficiency
by reducing the flux swing in L1.
at 500kHz. CT1 and T1 are wound on Magnetics, Inc. P-type
material toroids. L1 is wound on a Siemens N49 EFD core.
Magnetic components are carefully chosen for minimal loss
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
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
10k
0.15µF
4.7nF
VOUT
5V, 8A
VDD GATEH
0.1µF
NC
NC
FLT
EN
IN
VB
GATEL
SH+
MIC38C43
COMP VREF
6.8k
300k
4.3k
1000µF
Low ESR
470µF
25V
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
MIC38C42/3/4/5
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MIC38C42/3/4/5
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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)
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MIC38C42/3/4/5
MIC38C42/3/4/5
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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)
0.0040 (0.102)
0.010 (0.25)
0.007 (0.18)
0°–8°
0.197 (5.0)
0.189 (4.8)
0.050 (1.27)
0.016 (0.40)
SEATING
PLANE
0.064 (1.63)
0.045 (1.14)
0.244 (6.20)
0.228 (5.79)
8-Pin SOP (M)
0.122 (3.10)
0.112 (2.84)
0.199 (5.05)
0.187 (4.74)
DIMENSIONS:
INCH (MM)
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)
0.012 (0.03) R
0.039 (0.99)
0.0256 (0.65) TYP
0.035 (0.89)
0.021 (0.53)
8-Pin MSOP (MM)
PIN 1
DIMENSIONS:
INCHES (MM)
0.154 (3.90)
0.026 (0.65)
MAX)
0.193 (4.90)
0.050 (1.27) 0.016 (0.40)
TYP TYP
45°
0.006 (0.15)
3°–6°
0.244 (6.20)
0.228 (5.80)
0.344 (8.75)
0.337 (8.55)
SEATING
PLANE
0.057 (1.45)
0.049 (1.25)
14-Pin SOP (M)
MIC38C42/3/4/5
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Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
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.
© 2000 Micrel Incorporated
MIC38C42/3/4/5
12
August 2000
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