MIC5157BM [MICROCHIP]
Analog Circuit, 1 Func, PDSO14, SOIC-14;
| 型号： | MIC5157BM |
| 厂家： | 
MICROCHIP |
| 描述： | Analog Circuit, 1 Func, PDSO14, SOIC-14 光电二极管 |
| 文件： | 总13页 (文件大小：278K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC5156/5157/5158
Super LDO™ Regulator Controller
either 3.3V, 5.0V, or 12V. The MIC5158 can be configured
as a fixed 5V controller or programmed to any voltage from
1.3V to 36V using two external resistors.
General Description
The MIC5156, MIC5157, and MIC5158 Super Low-Dropout
(LDO) Regulator Controllers are single IC solutions for high-
current low-dropout linear voltage regulation. Super LDO™
Regulators have the advantages of an external N-channel
power MOSFET as the linear pass element.
The MIC5156 is available in an 8-pin DIP or SOIC. The
MIC5157 and MIC5158 are available in a 14-pin DIPor SOIC
which operate from –40°C to +85°C.
The MIC5156/7/8 family features a dropout voltage as low
as the R
of the external power MOSFET multiplied by
DS(ON)
Features
• 4.5mA typical operating current
• <1µA typical standby current
• Low external parts count
• Optional current limit (35mV typical threshold)
• 1% initial output voltage tolerance in most configurations
• 2% output voltage tolerance over temperature
• Fixed output voltages of 3.3V, 5.0V (MIC5156)
• Fixed output voltages of 3.3V, 5.0V, 12V (MIC5157)
• Programmable (1.3 to 36V) with 2 resistors (MIC5156/8)
• Internal charge pump voltage tripler (MIC5157/8)
• Enable pin to activate or shutdown the regulator
• Internal gate-to-source protective clamp
• All versions available in DIP and SOIC
the output current. The output current can be as high as the
largest MOSFETs can provide.
The MIC5156/7/8 family operates from 3V to 36V. The
MIC5156 requires an external gate drive supply to provide
the higher voltage needed to drive the gate of the external
MOSFET. The MIC5157 and MIC5158 each have an inter-
nal charge pump tripler to produce the gate drive voltage.
The tripler is capable of providing enough voltage to drive a
logic-level MOSFET to 3.3V output from a 3.5V supply and
is clamped to 17.5V above the supply voltage. The tripler
requires three external capacitors.
The regulator output is constant-current limited when the
controller detects 35mV across an optional external sense
resistor. An active-low open-collector flag indicates a low
voltage of 8% or more below nominal output. A shutdown
(low) signal to the TTL-compatible enable control reduces
controller supply current to less than 1µA while forcing the
output voltage to ground.
Applications
• Ultrahigh current ultralow dropout voltage regulator
• Constant high-current source
• Low parts count 5.0V to 3.3V computer supply
• Low noise/low-dropout SMPS post regulator
• High-current, current-limited switch
The MIC5156-3.3 and MIC5156-5.0 controllers have inter-
nally fixed output voltages. The MIC5156 [adjustable] output
is configured using two external resistors. The MIC5157 is a
fixed output controller which is externally configured to select
Typical Applications
+12V
1.0µF
0.1µF
0.1µF
Enable
Shutdown
4
3
2
1
7
6
5
4
3
2
1
MIC5157
MIC5156-3.3
5
6
7
8
8
9
10 11 12 13 14
0.1µF
Enable
3mΩ
RS
3mΩ
RS
Shutdown
VIN
5V
VOUT
3.3V, 10A
VOUT
3.3V, 10A
VIN
(3.61Vmin.)
CL*
47µF
CL*
47µF
47µF
47µF
RS = 0.035V /ILIMIT
RS = 0.035V /ILIMIT
*Improves transient
*Improves transient
SMP60N03-10L
response to load changes
IRLZ44 (Logic Level MOSFET) response to load changes
10A 5V to 3.3V Desktop Computer Regulator
10A Low-Dropout Voltage Regulator
Super LDO 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
August 2005
1
MIC5156/5157/5158
MIC5156/5157/5158
Micrel, Inc.
Ordering Information MIC5156
Part Number
Temperature
Range
Standard
Pb-Free
Voltage
3.3V
5.0V
Adj
Package
8-pin DIP
8-pin DIP
8-pin DIP
8-pin SOIC
8-pin SOIC
8-pin SOIC
MIC5156-3.3BN
MIC5156-5.0BN
MIC5156BN
MIC5156-3.3YN
MIC5156-5.0YN
MIC5156YN
–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
MIC5156-3.3BM
MIC5156-5.0BM
MIC5156BM
MIC5156-3.3YM
MIC5156-5.0YM
MIC5156YM
3.3V
5.0V
Adj
Ordering Information MIC5157
Part Number
Temperature
Range
Standard
Pb-Free
Voltage
Selectable
Selectable
Package
14-pin DIP
14-pin SOIC
MIC5157BN
MIC5157BM
MIC5157YN
MIC5157YM
–40°C to +85°C
–40°C to +85°C
Ordering Information MIC5158
Part Number
Temperature
Range
Standard
Pb-Free
Voltage
5.0V/Adj
5.0V/Adj
Package
14-pin DIP
14-pin SOIC
MIC5158BN
MIC5158BM
MIC5158YN
MIC5158YM
–40°C to +85°C
–40°C to +85°C
Pin Configuration
MIC5156
MIC5156-x.x
EN 1
8
7
6
5
EA
EN 1
8
7
6
5
S (Source)
D (Drain)
G (Gate)
VD D
FLAG 2
GND 3
D (Drain)
G (Gate)
VD D
FLAG 2
GND 3
VP
4
VP
4
MIC5157
MIC5158
5V 1
3.3V 2
FLAG 3
GND 4
14 EN
EA 1
5V FB 2
FLAG 3
GND 4
14 EN
13 S (Source)
12 D (Drain)
11 G (Gate)
10 VD D
13 S (Source)
12 D (Drain)
11 G (Gate)
10 VD D
VCP
5
VCP 5
C2– 6
C2+ 7
9
8
C1–
C2– 6
C2+ 7
9
8
C1–
C1+
C1+
MIC5156/5157/5158
2
August 2005
MIC5156/5157/5158
Micrel, Inc.
Pin Description MIC5156
Pin Number
Pin Name
Pin Function
1
2
EN
Enable (Input): TTL high enables regulator; TTL low shuts down regulator.
FLAG
Output Flag (Output): Open collector output is active (low) when VOUT is more
than 8% below nominal output. Circuit has 3% hysteresis.
3
4
GND
VP
Circuit ground.
N-channel Gate Drive Supply Voltage: User supplied voltage for driving the
gate of the external MOSFET.
5
VDD
Supply Voltage (Input): Supply voltage connection. Connect sense resis-
tor (RS) to VDD if current limiting used. Connect supply bypass capacitor to
ground near device.
6
7
G
D
Gate (Output): Drives the gate of the external MOSFET.
Drain and Current Limit (Input): Connect to external MOSFET drain and ex-
ternal sense resistor (current limit), or connect to VDD and external MOSFET
drain (no current limit).
8 (3.3V, 5V)
S
Source (Input): Top of internal resistive divider chain. Connect directly to the
load for best load regulation.
8 (adjustable)
EA
Error Amplifier (Input): Connect to external resistive divider.
Pin Description MIC5157, MIC5158
Pin Number
1 (MIC5157)
1 (MIC5158)
Pin Name
Pin Function
5V
EA
5V Configuration (Input): Connect to S (source) pin for 5V output.
Error Amplifier (Input): Connect to external resistive divider to obtain adjust-
able output.
2 (MIC5157)
2 (MIC5158)
3
3.3V
5VFB
FLAG
3.3V Configuration (Input): Connect to S (source) pin for 3.3V output.
5V Feedback (Input): Connect to EA for fixed 5V output.
Output Voltage Flag (Output): Open collector is active (low) when VOUT is 8%
or more below its nominal value.
4
5
6
GND
VCP
C2–
Circuit ground.
Voltage Tripler Output [Filter Capacitor]. Connect a 1 to 10µF capacitor to ground.
Charge Pump Capacitor 2: Second stage of internal voltage tripler. Connect a
0.1µF capacitor from C2+ to C2–.
7
8
C2+
C1+
Charge Pump Capacitor 2: See C2– pin 6.
Charge Pump Capacitor 1: First stage of internal voltage tripler. Connect a
0.1µF capacitor from C1+ to C1–.
9
C1–
VDD
Charge Pump Capacitor 1: See C1+ pin 8.
10
Supply Voltage (Input): Supply voltage connection. Connect sense resis-
tor (RS) to VDD if current limiting used. Connect supply bypass capacitor to
ground near device.
11
12
G
D
Gate (Output): Connect to External MOSFET gate.
Drain and Current Limit (Input): Connect to external MOSFET drain and ex-
ternal sense resistor (current limit), or connect to VDD and external MOSFET
drain (no current limit).
13 (MIC5157)
S
Source and 3.3V/5V Configuration: Top of internal resistor chain. Connect to
source of external MOSFET for 3.3V, 5V, and 12V operation. Also see 3.3V
and 5V pin descriptions.
13 (MIC5158)
14
S
Source (Input): Top of internal resistor chain. Connect to top of external resis-
tive divider and source of external MOSFET.
EN
Enable (Input): TTL high enables regulator; TTL low shuts down regulator.
August 2005
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MIC5156/5157/5158
MIC5156/5157/5158
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Input (V ).......................................................+38V
Ambient Temperature Range (T )
DD
A
MIC515xBM/BN...................................... –40°C to +85°C
Enable Input (V ) ..........................................–0.3V to 36V
EN
Junction Temperature (T )....................................... +150°C
Gate Output (V ) MIC5156 .........................................+55V
J
G
Thermal Resistance (θ )
Package
Charge Pump Node (V ) MIC5157/8 ........................+55V
JA
CP
MIC5156
MIC5157/8
Source Connection (V ) ...................................1.3 to +36V
S
DIP................................ 100°C/W .....................90°C/W
SOIC............................. 160°C/W ...................120°C/W
Flag (V
) ....................................................–0.3 to +40V
FLAG
Storage Temperature (T ) ........................ –65°C to +150°C
S
Lead Temperature (soldering 10 sec.)....................... 300°C
Electrical Characteristics(Note 5)
VDD = 5V, VEN = 5V; TA = 25°C; unless noted.
Symbol
Parameter
Condition
Min
Typ
Max
Units
VDD
Supply Voltage
3
36
V
IDD(ON)
IDD(OFF)
Supply Current MIC5156
Operating, VEN = 5V
Shutdown, VEN = 0V
2.7
0.1
10
5
mA
µA
IDD(ON)
IDD(OFF)
Supply Current MIC5157/8
Enable Input Threshold
Operating, VEN = 5V
Shutdown, VEN = 0V
4.5
0.1
10
5
mA
µA
VIH
VIL
High
Low
2.4
1.3
1.3
V
V
0.8
25
EN IB
VCP
fCP
Enable Input Bias Current
Max. Charge Pump Voltage
Charge Pump Frequency
VEN = 2.4V
20
µA
V
VCP – VDD, VDD > 10V
17.5
160
18.5
kHz
VOUT MAX Maximum Gate Drive Voltage
(MIC5157/8)
VSOURCE = 0V
V
V
V
DD = 3.5V
DD = 5V
DD = 12V
5
9
24
7.0
11.3
28
9
15
30
V
V
V
VOUT MIN
VLIM
Minimum Gate Drive Voltage
Current Limit Threshold
Source Voltage
VSOURCE > VOUT(NOM)
VDD – VD @ ILIM
1.0
35
V
28
42
mV
VS
Short G (gate) to (S) source, Note 4
MIC5156-3.3
MIC5156-5.0
MIC5157, 3.3V pin to S pin (3.3V config.)
MIC5157, 5V pin to S pin (5V config.)
MIC5157, VDD = 7V, (12V config.)
MIC5158, 5VFB pin to EA pin (5V config.)
3.267
4.950
3.250
4.950
11.70
4.925
3.3
5.0
3.3
5.0
12
3.333
5.050
3.350
5.050
12.30
5.075
V
V
V
V
V
V
5.0
VBG
Bandgap Reference Voltage
MIC5156 [adjustable] and MIC5158
1.222 1.235 1.248
V
mV
V
VLR
Output Voltage Line Regulation 5V < VDD < 15V, VOUT = 3.3V
Gate to Source Clamp
2
16.6
92
7
VGS MAX
VFT
14
20
Flag Comparator Threshold
Flag Comparator Hysteresis
Flag Comparator Sat. Voltage
% of nominal VSOURCE
% of nominal VSOURCE
IFLAG = 1mA
%
%
V
VFH
3
VSAT
0.09
0.2
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Note 4. Test configuration. External MOSFET not used.
Note 5. Specification for packaged product only.
MIC5156/5157/5158
4
August 2005
MIC5156/5157/5158
Micrel, Inc.
Typical Characteristics
3.3V Regulator Output
Voltage vs. Temperature
5.0V Regulator Output
Voltage vs. Temperature
MIC5157/8 Turn-On
Response Time for 3.3V
3.34
5.04
5.03
5.02
5.01
5.00
4.99
4.98
4.97
4.96
12
10
8
MOSFET = IRF540
VIN = 5V, IL = 0.5A
CC1 = CC2 = 0.1µF
CCP = 1µF
3.33
3.32
3.31
3.30
3.29
3.28
3.27
3.26
6
CL = 50µF
4
LOGIC
INPUT
2
3.3V
OUTPUT
0
-2
-0.2
-60 -30
0
30 60 90 120 150
-60 -30
0
30 60 90 120 150
0.0
0.2
0.4
0.6
TEMPERATURE (°C)
TEMPERATURE (°C)
TIME (ms)
MIC5157/8 On-State Supply
Current vs. Supply Voltage
MIC5157/8 On-State Supply
Current vs. Temperature
Off-State Supply Current
vs. Temperature
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
VDD = 5V
VDD = 5V
0
5
10 15 20 25 30
-60 -30
0
30 60 90 120 150
-60 -30
0
30 60 90 120 150
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
Charge-Pump Output Voltage
vs. Supply Voltage
Flag Output Voltage
vs. Temperature
Flag Output Voltage
vs. Flag Current
60
200
175
150
125
100
75
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
VDD = 5V
IFLAG = 1mA
VDD = 5V
50
40
30
20
10
0
50
25
0
0
5
10 15 20 25 30
-60 -30
0
30 60 90 120 150
0
2
4
6
8
10
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
FLAG SINK CURRENT (mA)
Enable Threshold Voltage
vs. Temperature
Enable Input Bias Current
vs. Enable Voltage
Current Limit Threshold
vs. Temperature
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
120
100
80
60
40
20
0
70
60
50
40
30
20
10
0
-60 -30
0
30 60 90 120 150
0
2
4
6
8
10 12 14 16
-60 -30
0
30 60 90 120 150
TEMPERATURE (°C)
ENABLE VOLTAGE (V)
TEMPERATURE (°C)
August 2005
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MIC5156/5157/5158
MIC5156/5157/5158
Micrel, Inc.
Block Diagram MIC5156
+12V Input
+5V Input
0.1µF
VP
VDD
EN
Internal
Bias
Enable
Shutdown
RS
3mΩ
12k
to all
internal blocks
1.235V
Bandgap
ILIMIT
Reference
Comparator
D (Drain)
[ ILIMIT
+5V Input
Q2
]
35mV
16.6V
G (Gate)
VOUT
Comparator
Q1
Error
Amp
SMP60N03-10L
FLAG
Switched
S* (Source)
Regulated
+3.3V Output
5V Load
75mV
17k†
10k
* fixed version only
† 3.3V = 17k, 5V = 32k
CL
GND
EA‡
‡ adjustable version only
Block Diagram with External Components
Fixed 3.3V Power Supply with 5.0V Load Switch
Block Diagram MIC5157
+5V Input
C3
1µF
0.1µF C1 0.1µF C2
C1+ C1– C2+ C2– VCP
VDD
EN
VCP
Clamp
Charge Pump
Tripler
Internal
Bias
Enable
Shutdown
RS
3mΩ
Oscillator
to all
niternal blocks
1.235V
Bandgap
Reference
ILIMIT
Comparator
D (Drain)
[ ILIMIT
]
35mV
16.6V
G (Gate)
VOUT
Error
Q1
IRFZ44
Amp
Comparator
FLAG
S (Source)*
Regulated
+3.3V Output
75mV
58k
15k
17k
10k
5V
CL
3.3V
GND
Block Diagram with External Components
Fixed 3.3V 10A Power Supply
MIC5156/5157/5158
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August 2005
MIC5156/5157/5158
Micrel, Inc.
Block Diagram MIC5158
+5V Input
C3
1µF
0.1µF C1 0.1µF C2
C1+ C1– C2+ C2– VCP
VDD
EN
VCP
Clamp
Charge Pump
Tripler
Internal
Bias
Enable
Shutdown
RS
3mΩ
Oscillator
to all
internal blocks
1.235V
Bandgap
Reference
ILIMIT
Comparator
D (Drain)
[ ILIMIT
]
35mV
16.6V
G (Gate)
VOUT
Comparator
Error
Amp
Q1
IRFZ44
FLAG
S (Source)
Regulated
+3.6V Output
75mV
5V
FB
32k
10k
CL
GND
19.1k
10.0k
EA
Block Diagram with External Components
Adjustable Power Supply, 3.6V Configuration
to-source enhancement voltage for an external N-channel
MOSFET(regulatorpasselement)placedbetweenthesupply
and the load. The gate-to-source voltage may vary from 1V
to 16V depending upon the supply and load conditions.
Functional Description
ASuper LDO Regulator is a complete regulator built around
Micrel’s Super LDO Regulator Controller.
Refer to Block Diagrams MIC5156, MIC5157, and
MIC5158.
Because the source voltage (output) approaches the drain
voltage (input) when the regulator is in dropout and the
MOSFET is fully enhanced, an additional higher supply
voltage is required to produce the necessary gate-to-source
enhancement. This higher gate drive voltage is provided by
an external gate drive supply (MIC5156) or by an internal
charge pump (MIC5157 and MIC5158).
Version Differences
The MIC5156 requires an external voltage for MOSFET gate
drive and is available in 3.3V fixed output, 5V fixed output, or
adjustable output versions. With 8-pins, the MIC5156 is the
smallest of the Super LDO Regulator Controllers.
The MIC5157 and MIC5158 each have an internal charge
pump which provides MOSFET gate drive voltage. The
MIC5157 has a selectable fixed output of 3.3V, 5V, or 12V.
The MIC5158 may be configured for a fixed 5V or adjustable
output.
Gate Drive Supply Voltage (MIC5156 only)
The gate drive supply voltage must not be more than 14V
above the supply voltage (V – V < 14V). The minimum
P
DD
necessary gate drive supply voltage is:
V = V + V + 1
P
OUT
GS
Enable (EN)
where:
V = gate drive supply voltage
With at least 3.0V on V , applying a TTL low to EN places
DD
P
the controller in shutdown mode. A TTL high on EN enables
the internal bias circuit which powers all internal circuitry. EN
must be pulled high if unused. The voltage applied to EN may
be as high as 36V.
V
V
= regulator output voltage
OUT
= gate-to-source voltage for full
GS
MOSFET gate enhancement
The controller draws less than 1µA in shutdown mode.
Gate Enhancement
The error amplifier uses the gate drive supply voltage to drive
the gate of the external MOSFET. The error amplifier output
can swing to within 1V of V .
P
The Super LDO Regulator Controller manages the gate-
August 2005
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MIC5156/5157/5158
MIC5156/5157/5158
Micrel, Inc.
Charge Pump (MIC5157/5158 only)
Note that the recovery time to repetitive load transients may
be affected with small pump capacitors.
Thechargepumptriplercreatesadcvoltageacrossreservoir
capacitorC3. ExternalcapacitorsC1andC2providethenec-
essary storage for the stages of the charge pump tripler.
Gate-to-Source Clamp
A gate-to-source protective voltage clamp of 16.6V protects
the MOSFET in the event that the output voltage is suddenly
forced to zero volts. This prevents damage to the external
MOSFET during shorted load conditions. Refer to “Charge
Pump” for normal clamp circuit operation.
The tripler’s approximate dc output voltage is:
V
≈ 3 (V – 1)
CP
DD
where:
V
V
= charge pump output voltage
= supply voltage
CP
The source connection required by the gate-to-source clamp
is not available on the adjustable version of the MIC5156.
DD
The V clamp circuit limits the charge pump voltage to 16V
Output Regulation
CP
aboveV bygatingthechargepumposcillatorONorOFFas
DD
At start-up, the error amplifier feedback voltage (EA), or
internal feedback on fixed versions, is below nominal when
compared to the internal 1.235V bandgap reference. This
forces the error amplifier output high which turns on exter-
nal MOSFET Q1. Once the output reaches regulation, the
controller maintains constant output voltage under changing
input and load conditions by adjusting the error amplifier
output voltage (gate enhancement voltage) according to the
feedback voltage.
required. The charge pump oscillator operates at 160kHz.
The error amplifier uses the charge pump voltage to drive
the gate of the external MOSFET. It provides a constant load
of about 1mA to the charge pump. The error amplifier output
can swing to within 1V of V
.
CP
Although the MIC5157/8 is designed to provide gate drive
using its internal charge pump, an external gate drive sup-
ply voltage can be applied to V . When using an external
CP
gate drive supply, V must not be forced more than 14V
Out-of-Regulation Detection
CP
higher than V
.
DD
When the output voltage is 8% or more below nominal, the
open-collector FLAG output (normally high) is forced low to
signal a fault condition. The FLAG output can be used to
signal or control external circuitry. The FLAG output can also
be used to shut down the regulator using the EN control.
When constant loads are driven, the ON/OFF switching of
the charge pump may be evident on the output waveform.
This is caused by the charge pump switching ON and rapidly
increasingthesupplyvoltagetotheerroramplifier.Theperiod
ofthissmallchargepumpexcitationisdeterminedbyanumber
of factors: the input voltage, the 1mA op-amp load, any dc
leakage associated with the MOSFET gate circuit, the size
of the charge pump capacitors, the size of the charge pump
reservoircapacitor,andthecharacteristicsoftheinputvoltage
and load. The period is lengthened by increasing the charge
pump reservoir capacitor (C3). The amplitude is reduced by
weakeningthechargepump—thisisaccomplishedbyreduc-
ing the size of the pump capacitors (C1 and C2). If this small
burst is a problem in the application, use a 10µF reservoir
capacitor at C3 and 0.01µF pump capacitors at C1 and C2.
Current Limiting
Super LDO Regulators perform constant-current limiting (not
foldback). To implement current limiting, a sense resistor
(R ) must be placed in the “power” path between V and
S
DD
D (drain).
If the voltage drop across the sense resistor reaches 35mV,
the current limit comparator reduces the error amplifier out-
put. The error amplifier output is decreased only enough to
reduce the output current, keeping the voltage across the
sense resistor from exceeding 35mV.
Application Information
MOSFET Selection
VIN
Standard N-channel enhancement-mode MOSFETs are ac-
ceptable for most Super LDO regulator applications.
G
S
Logic-level N-channel enhancement-mode MOSFETs may
be necessary if the external gate drive voltage is too low
(MIC5156),ortheinputvoltageistoolow,toprovideadequate
charge pump voltage (MIC5157/8) to enhance a standard
MOSFET.
MIC515x
GND
Circuit Layout
Figure 1a. Connections for Fixed Output
For the best voltage regulation, place the source, ground,
and error amplifier connections as close as possible to the
load. See figures (1a) and (1b).
MIC5156/5157/5158
8
August 2005
MIC5156/5157/5158
Micrel, Inc.
VIN
Adjustable Configurations
Micrel’s MIC5156 [adjustable] and MIC5158 require an ex-
ternal resistive divider to set the output voltage from 1.235V
to 36V. For best results, use a 10kΩ resistor for R2. See
equation (1) and figure (2).
G
S
MIC5157
or
MIC5158
EA
V
OUT
4
1)
GND
R
= 1 × 10 (
- 1)
1.235
1
G
S
Figure 1b. Connections for Adjustable Output
VOUT
MIC5157/8
R1
VIN
EA*
GND
R2
10k
G
*
MIC5156
Figure 2. Typical Resistive Divider
EA
GND
Input Filter Capacitor
TheSuperLDOrequiresaninputbypasscapacitorforaccom-
modating wide changes in load current and for decoupling
the error amplifier and charge pump.Amedium to large value
low-ESR (equivalent series resistance) capacitor is best,
mounted close to the device.
* Optional 16V zener diode
recommended in applications
whereVG is greater than 18V
Figure 1c. MIC5156 Connections for
Adjustable Output
Output Filter Capacitor
An output filter capacitor may be used to reduce ripple and
improve load regulation. Stable operation does not require
a large capacitor, but for transient load regulation the size of
the output capacitor may become a consideration. Common
aluminumelectrolyticcapacitorsperformnicely;verylow-ESR
capacitors are not necessary. Increased capacitance (rather
than reduced ESR) is preferred. The capacitor value should
be large enough to provide sufficient I = C × dV/dt current
consistent with the required transient load regulation quality.
Foragivenstepincreaseinloadcurrent,theoutputvoltagewill
drop by about dV = I × dt/C, where I represents the increase
in load current over time t. This relationship assumes that
all output current was being supplied via the MOSFET pass
device prior to the load increase. Small (0.01µF to 10µF) film
capacitors parallel to the load will further improve response
to transient loads.
MOSFET Gate-to-Source Protection
WhenusingtheadjustableversionoftheMIC5156,anexternal
16Vzenerdiodeplacedfromgate-to-sourceisrecommended
for MOSFET protection. All other versions of the Super LDO
regulator controller use the internal gate-to-source clamp.
Output Voltage Configuration
Fixed Configurations
The MIC5156-3.3 and MIC5156-5.0 are preset for 3.3V and
5.0V respectively.
TheMIC5157operatesat3.3Vwhenthe3.3Vpinisconnected
to the S (source) pin; 5.0V when the 5.0V pin is connected to
the S pin; or 12V if the 3.3V and 5.0V pins are open.
The MIC5158 operates at a fixed 5V (without an external
resistive divider) if the 5VFB pin is connected to EA.
Somelinearregulatorsspecifyaminimumrequiredoutputfilter
capacitance because the capacitor determines the dominant
pole of the system, and thereby stabilizes the system. This
is not the situation for the MIC5156/7/8; its dominant pole is
determined within its error amplifier.
August 2005
9
MIC5156/5157/5158
MIC5156/5157/5158
Micrel, Inc.
Gate Supply
VIN
Current Limiting
Current sensing requires a low-value series resistance (R )
s
between V and D (drain). Refer to the typical applications.
RS
DD
VG
EN
VDD
Enable
Shutdown
The internal current-limiting circuit limits the voltage drop
across the sense resistor to 35mV. Equation (2) provides the
sense resistor value required for a given maximum current.
35mV
D
G
S
MIC5156-x.x
GND
2)
R
=
S
I
LIM
where:
R = sense resistor value
S
I
= maximum output current
Figure 4a. High-Side Switch
LIM
Most current-limited applications require low-value resistors.
See Application Hints 21 and 25 for construction hints.
If a MIC5157 or MIC5158 is used and is shutdown for a
given time, the charge pump reservoir V will bleed off. If
CP
Non-Current-Limited Applications
rechargingthereservoircausesanunacceptabledelayinthe
load reaching its operating voltage, do not use the EN pin
for on/off control. Instead, use the MIC5158, hold EN high to
keep the charge pump in continuous operation, and switch
the MOSFET on or off by overriding the error amplifier input
as shown in figure (4b).
For circuits not requiring current limiting, do not use a sense
resistor between V and D (drain). See figure (3). The con-
DD
troller will not limit current when it does not detect a 35mV
drop from V to D.
DD
VIN
VIN
VDD
VDD
D
EN
G
S
MIC5158
G
S
MIC5156
EA
GND
Figure 3. No Current Limit
3.3V Microprocessor Applications
1N4148
Output Off
Output On
Figure 4b. Fast High-Side Switch
Battery Charger Application
Forcomputerdesignsthatuse3.3Vmicroprocessorswith5V
logic, the FLAG output can be used to suppress the 5V sup-
ply until the 3.3V output is in regulation. Refer to the external
components shown with the MIC5156 Block Diagram.
The MIC5158 may be used in constant-current applications
suchasbatterychargers.Seefigure(5).Theregulatorsupplies
a constant-current (35mV ÷ R3) until the battery approaches
the float voltage:
SMPS Post Regulator Application
A Super LDO regulator can be used as a post regulator for a
switch-modepowersupply.TheSuperLDOregulatorcanpro-
vide a significant reduction in peak-to-peak ripple voltage.
R1
V
= 1.235 (1 +
)
R2
FL
High-Current Switch Application
All versions of the MIC5156/7/8 may be used for current-lim-
ited, high-current, high-side switching with or without voltage
regulation. See figure (4a). Simply leave the “S” terminal
open. A 16V zener diode from the gate to the source of the
MOSFET protects the MOSFET from overdrive during fault
conditions.
where:
V
= float voltage
FL
At float voltage, the MOSFET is shut off. A trickle charge is
supplied by R4.
MIC5156/5157/5158
10
August 2005
MIC5156/5157/5158
Micrel, Inc.
VIN
Uninterruptible Power Supply
The MIC5157 and two N-channel MOSFETs provide battery
switching for uninterruptible power as shown in figure (6).
Two MOSFETs are placed source-to-source to prevent cur-
rent flow through their body diodes when switched off. The
Super LDO regulator is continuously enabled to achieve
fast battery switch-in. Careful attention must be paid to the
ac-line monitoring circuitry to ensure that the output voltage
does not fall below design limits while the battery is being
switched in.
R3
R4
VDD
D
G
S
EN
MIC5158
R1
R2
EA
GND
VDD
EN
D
G
S
D
Q1
Figure 5. Battery Charger Concept
G
S
S
MOSFET body diodes
shown for clarity
MIC5158
G
Q2
D
EA
GND
40V max.
1N4148
Line
Battery
AC
Line
Uninterruptable
DC
Off-line
Power Supply
Figure 6. UPS Power Supply Concept
August 2005
11
MIC5156/5157/5158
MIC5156/5157/5158
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 DIP (N)
8-Pin SOIC (M)
MIC5156/5157/5158
12
August 2005
MIC5156/5157/5158
Micrel, Inc.
.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 DIP (N)
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 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.
© 1999 Micrel, Inc.
August 2005
13
MIC5156/5157/5158
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