Micrel MIC38C42-1BM Bicmos current-mode pwm controller Datasheet

MIC38C42/3/4/5
Micrel, Inc.
MIC38C42/3/4/5
BiCMOS Current-Mode PWM Controllers
General Description
Features
The MIC38C4x are fixed frequency, high performance, current-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 efficiency, especially at lower supply voltages. The MIC38C4x also features
a trimmed oscillator discharge current and bandgap reference.
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 14pin devices separate the analog and power connections for
improved perfomance and power dissipation.
• 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)
35V
5V
Reference
VREF
8 (14)
(VD)
UVLO
(11)
†
Oscillator
RT/CT
4 (7)
FB
OUT
2R
2 (3)
2.5V
R
T
Q
S
R
Q
6 (10)
‡
(PGND)
(8)
*
COMP
1 (1)
GND* (AGND) ISNS
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
September 2007
1
M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
Ordering Information
Part Number*
Temperature Range
Package
Standard
Pb-Free
MIC38C42BN
MIC38C42YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C43BN
MIC38C43YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C44BN
MIC38C44YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C45BN
MIC38C45YN
-40°C to +85°C
8-pin Plastic DIP
MIC38C42-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C43-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C44-1BN
MIC38C44-1YN
-40°C to +85°C
14-pin Plastic DIP
MIC38C45-1BN
Contact Factory
-40°C to +85°C
14-pin Plastic DIP
MIC38C42BM
MIC38C42YM
-40°C to +85°C
8-pin SOIC
MIC38C43BM
MIC38C43YM
-40°C to +85°C
8-pin SOIC
MIC38C44BM
MIC38C44YM
-40°C to +85°C
8-pin SOIC
MIC38C45BM
MIC38C45YM
-40°C to +85°C
8-pin SOIC
MIC38C42BMM
MIC38C42YMM
-40°C to +85°C
8-pin MSOP
MIC38C43BMM
MIC38C43YMM
-40°C to +85°C
8-pin MSOP
MIC38C44BMM
MIC38C44YMM
-40°C to +85°C
8-pin MSOP
MIC38C45BMM
MIC38C45YMM
-40°C to +85°C
8-pin MSOP
MIC38C42-1BM
MIC38C42-1YM
-40°C to +85°C
14-pin SOIC
MIC38C43-1BM
MIC38C43-1YM
-40°C to +85°C
14-pin SOIC
MIC38C44-1BM
MIC38C44-1YM
-40°C to +85°C
14-pin SOIC
MIC38C45-1BM
MIC38C45-1YM
-40°C to +85°C
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
M9999-091107
Duty Cycle
Startup 8.4V
Minimum Operating 7.6V
Startup 14.5V
Minimum Operating 9V
0% to 96%
MIC38C43
MIC38C42
0% to 50%
MIC38C45
MIC38C44
2
September 2007
MIC38C42/3/4/5
Micrel, Inc.
Pin Configuration
MIC38C4x-1
COMP 1
MIC38C4x
COMP 1
8
VREF
2
7
VDD
ISNS 3
6
OUT
RT/CT 4
5
GND
FB
14 V R E F
NC
2
13 N C
FB
3
12 VDD
NC
4
11 VD
ISNS 5
10 OUT
6
9
AGND
RT/CT 7
8
P GND
NC
8-Pin DIP (N)
8-Pin SOIC (M)
8-Pin MSOP (MM)
14-Pin DIP (-1BN)
14-Pin SOIC (-1BM)
Pin Description
Pin Number
N, M, MM
Pin Number
-1BN, -1BM
Pin Name
1
1
COMP
2
NC
Not internally connected.
3
FB
Feedback (Input): Error amplifier input. Feedback is 2.5V at desired output
voltage.
4
NC
Not internally connected.
5
ISNS
6
NC
7
RT/CT
2
3
4
5
GND
Pin Function
Compensation: Connect external compensation network to modify the error
amplifier output.
Current Sense (Input): Current sense comparator input. Connect to current
sensing resistor or current transformer.
Not internally connected.
Timing Resistor/Timing Capacitor: Connect external RC network to select
switching frequency.
Ground: Combined analog and power ground.
8
PGND
Power Ground: N-channel driver transistor ground.
9
AGND
Analog Ground: Controller circuitry ground.
10
OUT
11
VD
Power Supply (Input): P-channel driver transistor supply input. Return to
power ground (PGND).
7
12
VDD
Analog Supply (Input): Controller circuitry supply input. Return to analog
ground (AGND).
13
NC
8
14
VREF
6
September 2007
Power Output: Totem-pole output.
Not internally connected.
5V Reference (Output): Connect external RC network.
3
M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
Absolute Maximum Ratings
Operating Ratings
Zener Current (VDD) ................................................... 30mA
Operation at ≥18V may require
special precautions (Note 6).
Supply Voltage (VDD), Note 6........................................ 20V
Switch Supply Voltage (VD) ........................................... 20V
Current Sense Voltage (VISNS) .......................–0.3V to 5.5V
Feedback Voltage (VFB) .................................–0.3V to 5.5V
Output Current, 38C42/3/4/5 (IOUT) ............................. 0.5A
Storage Temperature (TA)......................... –65°C to +150°C
Junction Temperature (TJ) ......................................... 150°C
Package Thermal Resistance
8-Pin Plastic DIP (θJA) .......................................125°C/W
8-Pin MSOP (θJA) ..............................................250°C/W
8-Pin SOIC (θJA) ................................................170°C/W
14-Pin Plastic DIP (θJA) ......................................90°C/W
14-Pin SOIC (θJA) ..............................................145°C/W
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
Output Voltage
TA = 25°C, IO = 1mA
4.90
5.00
5.10
V
Line Regulation
12V ≤ VDD ≤ 18V, IO = 5µA, Note 6
2
20
mV
Load Regulation
1 ≤ IO ≤ 20mA
1
25
mV
Temp. Stability
Note 1
Total Output Variation
Line, Load, Temp., Note 1
Output Noise Voltage
10Hz ≤ f ≤ 10kHz, TA = 25°C, Note 1
50
Long Term Stability
TA = 125°C, 1000 hrs., Note 1
5
25
mV
–30
–80
–180
mA
49
52
55
kHz
1.0
%
Reference Section
0.2
4.82
Output Short Circuit
mV/°C
5.18
V
µV
Oscillator Section
Initial Accuracy
TA = 25°C, Note 5
Voltage Stability
12 ≤ VDD ≤ 18V, Note 6
0.2
Temp. Stability
TMIN ≤ TA ≤ TMAX, Note 1
0.04
Clock Ramp
TA = 25°C, VRT/CT = 2V
Reset Current
TA = TMIN to TMAX
Amplitude
VRT/CT peak to peak
7.7
7.2
8.4
8.4
%/°C
9.0
9.5
1.9
mA
mA
Vp-p
Error Amp Section
Input Voltage
VCOMP = 2.5V
Input Bias Current
VFB = 5.0V
AVOL
2 ≤ VO ≤ 4V
65
90
dB
Unity Gain Bandwidth
Note 1
0.7
1.0
MHz
PSRR
12 ≤ VDD ≤ 18V
60
Output Sink Current
VFB = 2.7V, VCOMP = 1.1V
2
14
mA
Output Source Current
VFB = 2.3V, VCOMP = 5V
–0.5
–1
mA
VOUT High
VFB = 2.3V, RL = 15k to ground
5
6.8
V
VOUT Low
VFB = 2.7V, RL = 15k to VREF
M9999-091107
2.42
2.50
2.58
V
–0.1
–2
µA
dB
0.1
4
1.1
V
September 2007
MIC38C42/3/4/5
Parameter
Micrel, Inc.
Test Conditions
Min
Typ
Max
Units
Gain
Notes 2, 3
2.85
3.0
3.15
V/V
MaximumThreshold
VCOMP = 5V, Note 2
0.9
1
1.1
V
PSRR
12 ≤ VDD ≤ 18V, Note 2
Current Sense
70
dB
Input Bias Current
–0.1
–2
µA
Delay to Output
120
250
ns
Output
RDS(ON) High
RDS(ON) Low
ISOURCE = 200mA
ISINK = 200mA
20
11
Ω
Ω
Rise Time
TA = 25°C, CL = 1nF
40
80
ns
Fall Time
TA = 25°C, CL = 1nF
30
60
ns
Undervoltage Lockout
Start Threshold
Minimum Operating Voltage
MIC38C42/4
13.5
14.5
15.5
V
MIC38C43/5
7.8
8.4
9.0
V
MIC38C42/4
8
9
10
V
MIC38C43/5
7.0
7.6
8.2
V
MIC38C42/3
94
96
%
MIC38C44/5
46
50
%
Pulse Width Modulator
Maximum Duty Cycle
Minimum Duty Cycle
0
%
Total Standby Current
Start-Up Current
VDD = 13V for MIC38C42/44
50
200
µA
Operating Supply Current
VFB = VISNS = 0V
4.0
6.0
mA
Zener Voltage (VDD)
IDD = 25mA, Note 6
VDD = 7.5V for MIC38C43/45
30
37
V
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
5
M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
200pF
470pF
1nF
10
1.8nF
4.7nF
10nF
VDD = 15V
100
OUTPUT DEAD TIME (%)
RT RESISTANCE (kΩ)
100
MIC38C42/43 Output Dead Time
vs. Oscillator Frequency
Current Sense Amplifier
vs. Error Amplifier Output
1.2
1.0
125°C
0.8
0.6
25°C
0.4
-50°C
0.2
0
0
2
4
6
8
ERROR AMPLIFIER OUTPUT (V)
M9999-091107
4.7nF
200pF
10nF
470pF
1nF
1
1x104
VREF SHORT CURCUIT CURRENT (mA)
CURRENT SENSE AMP THRESHOLD (V)
1
1x104
1x105
5x105
OSCILLATOR FREQUENCY (Hz)
10
VDD = 15V
120
18nF
1x105
FREQUENCY (Hz)
1x106
Short-Circuit Reference
Current vs. Temperature
100
80
60
40
20
VDD = 15V
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
6
9.0
Oscillator Discharge
Current vs. Temperature
8.8
8.6
8.4
8.2
8.0
7.8
7.6
VDD = 15V
VOSC = 2V
7.4
7.2
7.0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
25
OUTPUT VOLTAGE (V)
Oscillator Frequency
Configuration
OSC. DISCHARGE CURRENT (mA)
Typical Characteristics
MIC38C4x
Output Waveform
20
15
10
5
0
-5
-10
-15
0.0
VD = 15V
CL = 1nF
0.2
0.4
0.6
TIME (µs)
0.8
1.0
September 2007
MIC38C42/3/4/5
Micrel, Inc.
Application Information
When designing high-frequency converters, avoid capacitive
and inductive coupling of the switching waveform into highimpedance circuitry such as the error amplifier, oscillator, and
current sense amplifier. Avoid long printed-circuit traces and
component leads. Locate oscillator and compensation circuitry
near the IC. Use high frequency decoupling capacitors on
VREF, and if necessary, on VDD. Return high di/dt currents
directly to their source and use large area ground planes.
Familiarity with 384x converter designs is assumed.
The MIC38C4x has been designed to be compatible with
384xA series controllers.
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). The reduced
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 VDD is greater
than 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
through L1. D5 supplies a regulated +12V to VDD once the
circuit is running.
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.
Using a high-value inductance for L1 and a low-ESR capacitor for C3 permits small capacitance with minimum output
ripple. This inductance value also improves circuit efficiency
by reducing the flux swing in L1.
Magnetic components are carefully chosen for minimal loss
at 500kHz. CT1 and T1 are wound on Magnetics, Inc. Ptype material toroids. L1 is wound on a Siemens N49 EFD
core.
Operating Current
Operating current has been reduced to 4mA compared to
11mA for a typical bipolar controller. The controller runs
cooler and the VDD hold-up capacitance required during
start-up may be reduced.
Output Driver
Complementary internal P- and N-channel MOSFETs produce rail-to-rail output voltages for better performance driving
external power MOSFETs. The driver transistor’s low onresistance 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 switching
frequency can approach 500kHz.
Design Precautions
When operating near 20V, circuit transients can easily exceed
the 20V absolute maximum rating, permanently damaging the
controller’s CMOS construction. To reduce transients, use
a 0.1µF low-ESR capacitor to next to the controller’s supply
VDD (or VD for ‘-1’ versions) and ground connections. Film
type capacitors, such as Wima MKS2, are recommended.
V IN
26V to 40V
R2
68k
D4
1N765B
0.1µF*
D2
M17Z105
1/4W
MKS2
C5
4.7µF
4.7Ω
R1
10
1/2W
C2
1000pF
L1 48µH
31DQ10
D1
C3
3.3µF
C4
0.1µF
0.1µF
6.8k
100k
1
D3
MBR030
VOUT
12V, 2A
Q1
IRF820
CT1
0.22µF
2
3
R4
18
4
MIC38C42
COM P V R E F
FB
ISNS
VDD
OU T
RT/CT GND
C7
200pF
R5
16k
8
D5
7
6
5
1N4001
T1
C8
0.1µF
6.19k
1%
1.62k
1%
*Locate near MIC38C42 supply pins
0.1µF
Figure 1. 500kHz, 25W, Buck Converter
September 2007
7
M9999-091107
MIC38C42/3/4/5
Micrel, Inc.
Test
Conditions
Line Regulation
VIN = 26V to 80V, IO = 2A
Load Regulation VIN = 48V, IO = 0.2A to 2A
Efficiency
Output Ripple
Symbol
Custom Coil1
ETS2
0.5%
CT1
4923
ETS 92420
0.6%
T1
4924
ETS 92419
4925
ETS 92421
Results
VIN = 48V, IO = 2A
90%
VIN = 48V, IO = 2A (20MHz BW)
L1
1.
2.
100mV
Synchronous Buck Converter
Refer to figure 2. This MIC38C43 synchronous buck converter
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 low-side MOSFET turns on when the high-side MOSFET is off, allowing current to return from ground. Current
flows through the low-side MOSFET in the source to drain
direction.
Custom Coils, Alcester, SD tel: (605) 934-2460
Energy Transformation Systems, Inc. tel: (415) 324-4949.
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 highside current sense inputs to provide overcurrent protection.
Refer to the MIC5020, MIC5021, and MIC5022 data sheets
for more information.
+12V
10k
MIC5022
0.15µF
VDD
0.1µF
6.8k
300k
4.7nF
4.3k
47k
2200
pF 3.3k
MIC38C43
COM P V R E F
VDD
FB
ISNS
VOUT
RT/CT
GND
NC
FL T
NC
EN
470µF
25V
NC
GATEH
VB
SMP60N06-14
5mΩ
35µH
V OUT
5V, 8A
GATEL
IN
SH+
CT
SH–
0.1µF*
MKS2
0.1µF
1000µF
Low ESR
SL+
GND
10k
S L–
*Locate near the MIC38C43 supply pins.
Figure 2. 100kHz, Synchronous Buck Converter
M9999-091107
8
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)
0.018 (0.57)
0.130 (3.30)
0.100 (2.54)
0.0375 (0.952)
0.380 (9.65)
0.320 (8.13)
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)
.060 (1.524)
.045 (1.143)
.400 (10.180)
.330 (8.362)
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
10
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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