Micrel MIC4574BWM 200khz simple 0.5a buck voltage regulator Datasheet

MIC4574
Micrel
MIC4574
200kHz Simple 0.5A Buck Voltage Regulator
General Description
Features
The MIC4574 is a series of easy to use fixed and adjustable
BiCMOS step-down (buck) switch-mode voltage regulators.
The 200kHz MIC4574 duplicates the pinout and function of
the 52kHz LM2574. The higher switching frequency may
allow up to a 2:1 reduction in output filter inductor size.
The MIC4574 is available in 3.3V, and 5V fixed output
versions or a 1.23V to 20V adjustable output version. Both
versions are capable of driving a 0.5A load with excellent line
and load regulation.
• Fixed 200kHz operation
• 3.3V, 5V, and adjustable output versions
• Voltage over specified line and load conditions:
Fixed version: ±3% max. output voltage
Adjustable version: ±2% max. feedback voltage
• Guaranteed 0.5A switch current
• Wide 4V to 24V input voltage range
• Wide 1.23V to 20V output voltage range
• Requires minimum external components
• < 200µA typical shutdown mode
• 75% efficiency (adjustable version > 75% typ.)
• Standard inductors and capacitors are
25% of typical LM2574 values
• Thermal shutdown
• Overcurrent protection
• 100% electrical thermal limit burn-in
The feedback voltage is guaranteed to ±2% tolerance for
adjustable versions, and the output voltage is guaranteed to
±3% for fixed versions, within specified voltages and load
conditions. The oscillator frequency is guaranteed to ±10%.
In shutdown mode, the regulator draws less than 200µA
standby current. The regulator performs cycle-by-cycle
current limiting and thermal shutdown for protection under
fault conditions.
This series of simple switch-mode regulators requires a
minimum number of external components and can operate
using a standard series of inductors. Frequency compensation is provided internally.
Applications
•
•
•
•
•
Simple high-efficiency step-down (buck) regulator
Efficient preregulator for linear regulators
On-card switching regulators
Positive-to-negative converter (inverting buck-boost)
Isolated flyback converter using minimum external
components
• Negative boost converter
The MIC4574 is available in DIP (N) and SOIC (WM) packages for the industrial temperature range.
Typical Applications
Shutdown
Enable
3
8V to 24V
5
C1
47µF
35V
SHDN
SW
MIC4574-5.0BN
FB
VIN
SGND PGND
2
L1
7
5.0V/0.5A
100µH
1
D1
1N5819
4
C2
220µF
16V
Fixed Regulator
Shutdown
Enable
6V to 24V
C1
10µF
35V
5
10
SHDN
SW
MIC4574BWM
FB
VIN
SGND PGND
4
6
L1
12
100µH
3
D1
3.3V/0.5A
R2
2.49k
1%
R1
1.50k
1%
C3
3300pF
C2
330µF
6.3V
MBRS130LT3
Adjustable Regulator
4-92
April 1998•
MIC4574
Micrel
Ordering Information
Part Number
Voltage
Temperature Range
Package
MIC4574-3.3BN
3.3V
–40°C to +85°C
8-pin DIP
MIC4574-5.0BN
5.0V
–40°C to +85°C
8-pin DIP
MIC4574BN
MIC4574-3.3BWM
MIC4574-5.0BWM
MIC4574BWM
Adjustable
–40°C to +85°C
8-pin DIP
3.3V
–40°C to +85°C
14-lead SOIC
5.0V
–40°C to +85°C
14-lead SOIC
Adjustable
–40°C to +85°C
14-lead SOIC
Pin Configuration
NC 1
14 NC
NC 2
13 NC
FB 3
12 SW
FB 1
8
NC
SGND 4
11 NC
SGND 2
7
SW
SHDN 5
10 VIN
SHDN 3
6
NC
PGND 6
9 NC
PGND 4
5
VIN
NC 7
8 NC
8-Pin DIP (N)
14-Lead Wide SOIC (WM)
Pin Description
Pin Number
N Package
Pin Number
WM Package
Pin Name
1
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
2
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
1
3
FB
Feedback (Input): Output voltage feedback to regulator. Connect to output of
supply for fixed versions. Connect to 1.23V tap of resistive divider for
adjustable versions.
2
4
SGND
Signal Ground
3
5
SHDN
Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts
down regulator.
4
6
PGND
Power Ground
7
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
8
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
9
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
10
VIN
Supply Voltage (Input): Unregulated +4V to +24V supply voltage.
11
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
7
12
SW
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
8
13
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
14
NC
Not internally connected. Solder to printed circuit for maximum heat transfer.
5
April 1998•
Pin Function
4-93
4
MIC4574
Micrel
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (VIN) Note 1 ....................................... +40V
Shutdown (VSHDN) ....................................... –0.3V to +36V
Output Switch (VSW) steady state ................................. –1V
Junction Temperature (TJ) ...................................... +150°C
Storage Temperature ............................... –65°C to +150°C
Supply Voltage (VIN) ................................................... +24V
Package Thermal Resistance
θJA Plastic DIP .................................................. 130°C/W
θJC SOIC ........................................................... 120°C/W
Electrical Characteristics
VIN =12V; ILOAD = 100mA; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Parameter
Condition
Min
Typ
Max
Units
1.217
1.230
1.243
V
1.193
1.180
1.230
1.267
1.280
V
V
MIC4574 [Adjustable]
Feedback Voltage
Feedback Voltage
8V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A
Efficiency
ILOAD = 0.5A, VOUT = 5V
77
Feedback Bias Current
%
50
100
500
nA
nA
3.234
3.3
3.366
V
3.168
3.135
3.3
3.432
3.465
V
V
MIC4574-3.3
Output Voltage
Output Voltage
6V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A
Efficiency
72
%
MIC4574-5.0
Output Voltage
Output Voltage
8V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A
4.900
5.0
5.100
V
4.800
4.750
5.0
5.200
5.250
V
V
Efficiency
77
%
MIC4574 / -3.3 / -5.0
Oscillator Frequency
180
Saturation Voltage
IOUT = 0.5A
Maximum Duty Cycle (On)
FB connected to 0V
Current Limit
Peak Current, tON ≤ 3µs
Output Leakage Current
VIN = 24V, FB connected to 6V
Output = 0V
Output = –1V
SHDN = 5V (regulator off)
SHDN Input Logic Level
VOUT = 0V (regulator off)
1
1.3
1.5
V
V
0.7
0.65
1.0
1.6
1.8
A
A
0
7.5
2
30
mA
mA
5
10
mA
50
200
µA
2.2
2.4
SHDN = 5V (regulator off)
SHDN = 0V (regulator on)
kHz
95
VOUT = 3.3V or 5V (regulator on)
SHDN Input Current
220
90
Quiescent Current
Standby Quiescent Current
200
–10
%
1.4
V
V
1.2
1.0
0.8
V
V
4
0.01
30
10
µA
µA
General Note: Devices are ESD protected, however, handling precautions are recommended.
Note 1:
The MIC4574 is not guaranteed to survive a short circuit to ground for input voltage above 24V.
4-94
April 1998•
MIC4574
Micrel
Block Diagrams
+24V max.
VIN
Shutdown
Enable
SHDN
CIN
Internal
Regulator
Thermal
Shutdown
200kHz
Oscillator
Current
Limit
Driver
Comparator
L1
SW
VOUT
0.5A
Switch
D1
COUT
1.23V
Bandgap
Error
Amp.
R1
FB
R2
MIC4574-x.x
GND
4
Block Diagram with External Components
Fixed Step-Down Regulator
+24V max.
VIN
Shutdown
Enable
SHDN
CIN
Internal
Regulator
Thermal
Shutdown
200kHz
Oscillator
VOUT
Current
Limit
R1
Comparator
Driver
V REF
R2
R1
+ 1
R2
VOUT
VREF
1
L1
SW
VOUT
0.5A
Switch
D1
COUT
Error
Amp.
1.23V
Bandgap
R1
FB
MIC4574 [Adjustable]
GND
Block Diagram with External Components
Adjustable Step-Down Regulator
April 1998•
4-95
R2
MIC4574
Micrel
Functional Description
A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
inverting input) causes the comparator to detect only the
peaks of the sawtooth, reducing the duty cycle of the comparator output. A lower feedback voltage increases the duty
cycle.
Output Switching
The MIC4574 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
Supply Voltage
The MIC4574 operates from a +4V to +24V unregulated
input. Highest efficiency operation is from a supply voltage
below +15V.
Enable/Shutdown
The shutdown (SHDN) input is TTL compatible. Ground the
input if unused. A logic-low enables the regulator. A logichigh shuts down the internal regulator which reduces the
current to typically 50µA.
When the internal switch is on, an increasing current flows
from the supply VIN, through external storage inductor L1, to
output capacitor COUT and the load. Energy is stored in the
inductor as the current increases with time.
When the internal switch is turned off, the collapse of the
magnetic field in L1 forces current to flow through fast
recovery diode D1, charging COUT.
Feedback
Fixed versions of the regulator have an internal resistive
divider from the feedback (FB) pin. Connect FB directly to the
output line.
Output Capacitor
External output capacitor COUT provides stabilization and
reduces ripple.
Return Paths
Adjustable versions require an external resistive voltage
divider from the output voltage to ground, connected from the
1.23V tap to FB.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 200kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.
During the on portion of the cycle, the output capacitor and
load currents return to the supply ground. During the off
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.
Applications Information
The applications circuits that follow have been constructed
and tested. Refer to Application Note 15 for additional
information, including efficiency graphs and manufacturer’s
addresses and telephone numbers for most circuits.
L1
3
6V to 24V
5
C1
47µF
35V
SHDN
MIC4574-3.3BN
FB
VIN
SGND PGND
2
C1
C2
D1
L1
SW
Nichicon
Nichicon
Motorola
Sumida
4
For a mathematical approach to component selection and
circuit design, refer to Application Note 14.
3.3V/0.5A
7
3
100µH
8V to 24V
C2
220µF
16V
1
D1
1N5819
C1
47µF
35V
16V to 24V
C1
33µF
63V
5
2
C1
C2
D1
L1
SW
MIC4574BN
VIN
SGND
Nichicon
Nichicon
Motorola
Sumida
Nichicon
Nichicon
Motorola
Sumida
4
7
L1
5.0V/0.5A
100µH
1
D1
1N5819
C2
220µF
16V
UPL1J470MEH, ESR = 0.34Ω
UPL1C221MPH, ESR = 0.16Ω
1N5819
RCH875-101K, DCR = 0.28Ω
Figure 2. 8V–24V to 5V/0.5A Buck Converter
Through Hole
Figure 1. 6V–24V to 3.3V/0.5A Buck Converter
Through Hole
SHDN
SW
MIC4574-5.0BN
FB
VIN
SGND PGND
2
C1
C2
D1
L1
UPL1V470MEH, ESR = 0.34Ω
UPL1C221MPH, ESR = 0.16Ω
1N5819
RCH875-101K, DCR = 0.28Ω
3
5
SHDN
FB
PGND
7
L1
220µH
1
MBR160
4
12V/0.5A
R2
13.0k
1%
R1
1.50k
1%
C2
220µF
16V
UPL1J330MEH, ESR = 0.35Ω
UPL1C221MPH, ESR = 0.16Ω
MBR160
RCH106-221K, DCR = 0.78Ω
Figure 3. 16V–24V to 12V/0.5A Buck Converter
Through Hole
4-96
April 1998•
MIC4574
Micrel
5
6V to 24V
SHDN
SW
MIC4574BWM
VIN
FB
SGND PGND
10
C1
10µF
35V
4
L1
12
3
R2
2.49k
1%
C3
3300pF
L1
C2
330µF
6.3V
R1
1.50k
1%
D1
6
3.3V/0.5A
5
100µH
6V to 24V
10
C1
68µF
35V
SHDN
SW
MIC4574-3.3BWM
FB
VIN
SGND PGND
4
3.3V/0.5A
12
100µH
C2
470µF
16V
3
D1
MBRS130LT3
6
MBRS130LT3
C1
C2
D1
L1
AVX
AVX
Motorola
Coiltronics
TPSD106M035R0300, ESR = 0.3Ω
TPSE337M006R0100, ESR = 0.1Ω
MBRS130LT3
CTX100-2P, DCR = 0.541Ω
C1
C2
D1
L1
Figure 4. 6V–24V to 3.3V/0.5A Buck Converter
Low-Profile Surface Mount
5
8V to 24V
SHDN
SW
MIC4574BWM
FB
VIN
SGND PGND
10
C1
10µF
35V
4
L1
12
100µH
3
35CV168GX, ESR = 0.34Ω
16CV470GX, ESR = 0.17Ω
MBRS130LT3
DO3316P-104, DCR = 0.23Ω
Figure 7. 6V–24V to 3.3V/0.5A Buck Converter
Low-Cost Surface Mount
5V/0.5A
R2
3.01k
1%
L1
5
C3
3300pF
C2
220µF
10V
R1
1.00k
1%
D1
6
Sanyo
Sanyo
Motorola
Coilcraft
8V to 24V
10
C1
68µF
35V
SHDN
SW
MIC4574-5.0BWM
FB
VIN
SGND PGND
4
5V/0.5A
12
100µH
3
D1
MBRS130LT3
6
C2
470µF
16V
MBRS130LT3
C1
C2
D1
L1
AVX
AVX
Motorola
Coiltronics
TPSD106M035R0300, ESR = 0.3Ω
TPSE227M010R0100, ESR = 0.1Ω
MBRS130LT3
CTX100-2P, DCR = 0.541Ω
C1
C2
D1
L1
Figure 5. 8V–24V to 5V/0.5A Buck Converter
Low-Profile Surface Mount
5
16V to 24V
10
C1
10µF
50V
SHDN
MIC4574BWM
FB
VIN
SGND PGND
4
C1
C2
D1
L1
SW
6
12
L1
250µH
3
D1
SS16
C3
3300pF
R1
1.50k
1%
C2
68µF
20V
Tokin
C55Y5U1H106Z
AVX
TPSE686M020R0150, ESR = 0.15Ω
General Instruments SS16
Coiltronics CTX250-4P, DCR = 0.434Ω
5
16V to 24V
10
C1
47µF
50V
SHDN
SW
MIC4574BWM
FB
VIN
SGND PGND
4
C1
C2
D1
L1
Figure 6. 16V–24V to 12V/0.5A Buck Converter
Low-Profile Surface Mount
April 1998•
35CV168GX, ESR = 0.34Ω
16CV470GX, ESR = 0.17Ω
MBRS130LT3
DO3316P-104, DCR = 0.23Ω
Figure 8. 8V–24V to 5V/0.5A Buck Converter
Low-Cost Surface Mount
12V/0.5A
R2
13.0k
1%
Sanyo
Sanyo
Motorola
Coilcraft
6
12
L1
220µH
3
D1
SS16
12V/0.5A
R2
13.0k
1%
R1
1.50k
1%
C2
470µF
16V
Nichicon UUX1H470MNT1GS, ESR = 0.4Ω
Sanyo
16CV470GX, ESR = 0.17Ω
General Instruments SS16
Coilcraft
DO3316-224, DCR = 0.53Ω
Figure 9. 16V–24V to 12V/0.5A Buck Converter
Low-Cost Surface Mount
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