MIC5156I5157I5158 IIIIIIIIEL® %' MI r'fi ‘31” T A} i Lani __ l I c ‘T a c a -1 _i 1 5 ; Wm SMPsuNflarlflL response to mad changes Q-I I+ Q-I I+ August 2005 ’l MICS156/5157/5158
August 2005 1 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
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.
The MIC5156 is available in an 8-pin DIP or SOIC. The
MIC5157 and MIC5158 are available in a 14-pin DIP or SOIC
which operate from –40°C to +85°C.
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
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
10A 5V to 3.3V Desktop Computer Regulator
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 MIC5156/7/8 family features a dropout voltage as low
as the RDS(ON) of the external power MOSFET multiplied by
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.
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
1234
14131211
567
10
98
MIC5157
C
2+
C
2–
VC
P
G
ND
F
LAG
3
.3V
5
V
C
1+
C
1
VD
D
G
D
S
E
N
VOUT
3.3V, 10A
VIN
(3.61Vmin.)
0.1µF
1.0µF
0.1µF
RS
RS = 0.035V /ILIMIT
3m
IRLZ44 (Logic Level MOSFET)
CL*
47µF
*Improves transient
response to load changes
Enable
Shutdown
47µF
10A Low-Dropout Voltage Regulator
123
876
4
5
MIC5156-3.3
V
P
G
ND
F
LAG
E
N
V
D
D
G
D
S
V
OU T
3.3V, 10A
V
IN
5V
0.1µF
R
S
R
S
= 0.035V /I
LIMIT
3m
SMP60N03-10L
C
L
*
47µF
*Improves transient
response to load changes
+12V
Enable
Shutdown
47µF
Typical Applications
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
_l__l__l__l_ _l__l__l__l__l__l__l_ M|C5156 U MIC5158 U _|__|__|__|_ _|__|__|__|__|__|__|_ _l__l__l__l_ _l__l__l__l__l__l__l_ U MICS156 x x U M|C5157 _|__|__|__|_ _|__|__|__|__|__|__|_
MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 2 August 2005
Pin Configuration
Ordering Information MIC5156
Part Number Temperature
Standard Pb-Free Voltage Range Package
MIC5156-3.3BN MIC5156-3.3YN 3.3V –40°C to +85°C 8-pin DIP
MIC5156-5.0BN MIC5156-5.0YN 5.0V –40°C to +85°C 8-pin DIP
MIC5156BN MIC5156YN Adj –40°C to +85°C 8-pin DIP
MIC5156-3.3BM MIC5156-3.3YM 3.3V –40°C to +85°C 8-pin SOIC
MIC5156-5.0BM MIC5156-5.0YM 5.0V –40°C to +85°C 8-pin SOIC
MIC5156BM MIC5156YM Adj –40°C to +85°C 8-pin SOIC
Ordering Information MIC5157
Part Number Temperature
Standard Pb-Free Voltage Range Package
MIC5157BN MIC5157YN Selectable –40°C to +85°C 14-pin DIP
MIC5157BM MIC5157YM Selectable –40°C to +85°C 14-pin SOIC
Ordering Information MIC5158
Part Number Temperature
Standard Pb-Free Voltage Range Package
MIC5158BN MIC5158YN 5.0V/Adj –40°C to +85°C 14-pin DIP
MIC5158BM MIC5158YM 5.0V/Adj –40°C to +85°C 14-pin SOIC
1
2
3
4
EN
FLAG
S (Source)
GND
VP
D (Drain)
VD D
G (Gate)
8
7
6
5
MIC5156-x.x
1
2
3
4
EA
5V FB
EN
FLAG
GND
S (Source)
G (Gate)
D (Drain)
14
13
12
11
MIC5158
5
6
7
VC P
C2
C2+
VD D
C1+
C1
10
9
8
1
2
3
4
5V
3.3V
EN
FLAG
GND
S (Source)
G (Gate)
D (Drain)
14
13
12
11
MIC5157
5
6
7
VC P
C2
C2+
VD D
C1+
C1
10
9
8
1
2
3
4
EN
FLAG
GND
VP
D (Drain)
VD D
G (Gate)
8
7
6
5
MIC5156
EA
August 2005 3 M|05156l5157l5158
August 2005 3 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
Pin Description MIC5156
Pin Number Pin Name Pin Function
1 EN Enable (Input): TTL high enables regulator; TTL low shuts down regulator.
2 FLAG Output Flag (Output): Open collector output is active (low) when VOUT is more
than 8% below nominal output. Circuit has 3% hysteresis.
3 GND Circuit ground.
4 VP 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 G Gate (Output): Drives the gate of the external MOSFET.
7 D 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 Pin Name Pin Function
1 (MIC5157) 5V 5V Configuration (Input): Connect to S (source) pin for 5V output.
1 (MIC5158) EA Error Amplifier (Input): Connect to external resistive divider to obtain adjust-
able output.
2 (MIC5157) 3.3V 3.3V Configuration (Input): Connect to S (source) pin for 3.3V output.
2 (MIC5158) 5V FB 5V Feedback (Input): Connect to EA for fixed 5V output.
3 FLAG Output Voltage Flag (Output): Open collector is active (low) when VOUT is 8%
or more below its nominal value.
4 GND Circuit ground.
5 VCP
Voltage Tripler Output [Filter Capacitor]. Connect a 1 to 10µF capacitor to ground.
6 C2– Charge Pump Capacitor 2: Second stage of internal voltage tripler. Connect a
0.1µF capacitor from C2+ to C2–.
7 C2+ Charge Pump Capacitor 2: See C2– pin 6.
8 C1+ Charge Pump Capacitor 1: First stage of internal voltage tripler. Connect a
0.1µF capacitor from C1+ to C1–.
9 C1– Charge Pump Capacitor 1: See C1+ pin 8.
10 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.
11 G Gate (Output): Connect to External MOSFET gate.
12 D 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) S Source (Input): Top of internal resistor chain. Connect to top of external resis-
tive divider and source of external MOSFET.
14 EN Enable (Input): TTL high enables regulator; TTL low shuts down regulator.
MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 4 August 2005
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) Supply Current MIC5156 Operating, VEN = 5V 2.7 10 mA
IDD(OFF) Shutdown, VEN = 0V 0.1 5 µA
IDD(ON) Supply Current MIC5157/8 Operating, VEN = 5V 4.5 10 mA
IDD(OFF) Shutdown, VEN = 0V 0.1 5 µA
VIH Enable Input Threshold High 2.4 1.3 V
VIL Low 1.3 0.8 V
EN IB Enable Input Bias Current VEN = 2.4V 20 25 µA
VCP Max. Charge Pump Voltage VCP – VDD, VDD > 10V 17.5 18.5 V
fCP Charge Pump Frequency 160 kHz
VOUT MAX Maximum Gate Drive Voltage VSOURCE = 0V
(MIC5157/8) VDD = 3.5V 5 7.0 9 V
VDD = 5V 9 11.3 15 V
VDD = 12V 24 28 30 V
VOUT MIN Minimum Gate Drive Voltage VSOURCE > VOUT(NOM) 1.0 V
VLIM Current Limit Threshold VDD – VD @ ILIM 28 35 42 mV
VS Source Voltage Short G (gate) to (S) source, Note 4
MIC5156-3.3 3.267 3.3 3.333 V
MIC5156-5.0 4.950 5.0 5.050 V
MIC5157, 3.3V pin to S pin (3.3V config.) 3.250 3.3 3.350 V
MIC5157, 5V pin to S pin (5V config.) 4.950 5.0 5.050 V
MIC5157, VDD = 7V, (12V config.) 11.70 12 12.30 V
MIC5158, 5V FB pin to EA pin (5V config.) 4.925 5.0 5.075 V
VBG Bandgap Reference Voltage MIC5156 [adjustable] and MIC5158 1.222 1.235 1.248 V
VLR Output Voltage Line Regulation 5V < VDD < 15V, VOUT = 3.3V 2 7 mV
VGS MAX Gate to Source Clamp 14 16.6 20 V
VFT Flag Comparator Threshold % of nominal VSOURCE 92 %
VFH Flag Comparator Hysteresis % of nominal VSOURCE 3 %
VSAT Flag Comparator Sat. Voltage IFLAG = 1mA 0.09 0.2 V
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.
Absolute Maximum Ratings (Note 1)
Supply Input (VDD) .......................................................+38V
Enable Input (VEN) ..........................................–0.3V to 36V
Gate Output (VG) MIC5156 ......................................... +55V
Charge Pump Node (VCP) MIC5157/8 ........................ +55V
Source Connection (VS) ...................................1.3 to +36V
Flag (VFLAG) ....................................................–0.3 to +40V
Storage Temperature (TS) ........................ –65°C to +150°C
Lead Temperature (soldering 10 sec.) ....................... 300°C
Operating Ratings (Note 2)
Ambient Temperature Range (TA)
MIC515xBM/BN ...................................... –40°C to +85°C
Junction Temperature (TJ) ....................................... +150°C
Thermal Resistance (θJA)
Package MIC5156 MIC5157/8
DIP ................................ 100°C/W ..................... 90°C/W
SOIC ............................. 160°C/W ................... 120°C/W
August 2005 5 MIC5156/5157/5158
August 2005 5 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
Typical Characteristics
.sv Input 1—0 I m G 4
MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 6 August 2005
Block Diagram MIC5156
EN Enable
Shutdown
1.235V
Bandgap
Reference
Internal
Bias
Error
Amp
75mV
35mV
GND
S* (Source)
16.6V
ILIMIT
Comparator D (Drain)
[ ILIMIT ]
G (Gate)
FLAG
VPVDD
VOUT
Comparator
10k
to all
internal blocks
EA
17k
Regulated
+3.3V Output
+12V Input +5V Input
+5V Input
RS
3m
0.1µF
Q2 Q1
SMP60N03-10L
Switched
5V Load
12k
* fixed version only
3.3V = 17k, 5V = 32k
adjustable version only
CL
Block Diagram MIC5157
Block Diagram with External Components
Fixed 3.3V Power Supply with 5.0V Load Switch
Block Diagram with External Components
Fixed 3.3V 10A Power Supply
1.235V
Bandgap
Reference
V
C P
Clamp
Internal
Bias
Error
Amp
75mV
35mV
GND
S (Source)*
I
LIMIT
Comparator D (Drain)
[ I
LIMIT
]
G (Gate)
V
C P
V
DD
V
OU T
Comparator
to all
internal blocks
3.3V
Regulated
+3.3V Output
+5V Input
Q1
IRFZ44
R
S
3m
1µF
16.6V
10k
58k
15k
17k
5V
Oscillator Charge Pump
Tripler
C1+ C1 C2+ C2
0.1µF 0.1µF
C1 C2
C3
FLAG
EN
Enable
Shutdown
C
L
.5v mm a < :i="" august="" 2005="" 7="" mic5156/5157/5158="">
August 2005 7 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
Functional Description
A Super LDO Regulator is a complete regulator built around
Micrel’s Super LDO Regulator Controller.
Refer to Block Diagrams MIC5156, 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.
Enable (EN)
With at least 3.0V on VDD, applying a TTL low to EN places
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.
The controller draws less than 1µA in shutdown mode.
Gate Enhancement
The Super LDO Regulator Controller manages the gate-
1.235V
Bandgap
Reference
VC P
Clamp
Internal
Bias
Error
Amp
75mV
35mV
EA
S (Source)
ILIMIT
Comparator D (Drain)
[ ILIMIT ]
G (Gate)
VC P VDD
VOUT
Comparator
to all
internal blocks
GND
Regulated
+3.6V Output
+5V Input
Q1
IRFZ44
RS
3m
1µF
16.6V
32k
10k
5V
FB
Oscillator Charge Pump
Tripler
C1+ C1 C2+ C2
0.1µF 0.1µF
C1 C2
C3
FLAG
19.1k
10.0k
EN Enable
Shutdown
CL
Block Diagram MIC5158
Block Diagram with External Components
Adjustable Power Supply, 3.6V Configuration
to-source enhancement voltage for an external N-channel
MOSFET (regulator pass element) placed between the supply
and the load. The gate-to-source voltage may vary from 1V
to 16V depending upon the supply and load conditions.
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).
Gate Drive Supply Voltage (MIC5156 only)
The gate drive supply voltage must not be more than 14V
above the supply voltage (VP VDD < 14V). The minimum
necessary gate drive supply voltage is:
VP = VOUT + VGS + 1
where:
VP = gate drive supply voltage
VOUT = regulator output voltage
VGS = gate-to-source voltage for full
MOSFET 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 VP
.
MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 8 August 2005
Charge Pump (MIC5157/5158 only)
The charge pump tripler creates a dc voltage across reservoir
capacitor C3. External capacitors C1 and C2 provide the nec-
essary storage for the stages of the charge pump tripler.
The tripler’s approximate dc output voltage is:
VCP ≈ 3 (VDD – 1)
where:
VCP = charge pump output voltage
VDD = supply voltage
The VCP clamp circuit limits the charge pump voltage to 16V
above VDD by gating the charge pump oscillator ON or OFF as
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 VCP
.
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 VCP . When using an external
gate drive supply, VCP must not be forced more than 14V
higher than VDD.
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
increasing the supply voltage to the error amplifier. The period
of this small charge pump excitation is determined by a number
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
reservoir capacitor, and the characteristics of the input voltage
and load. The period is lengthened by increasing the charge
pump reservoir capacitor (C3). The amplitude is reduced by
weakening the charge pump—this is accomplished by reduc-
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.
Note that the recovery time to repetitive load transients may
be affected with small pump capacitors.
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 source connection required by the gate-to-source clamp
is not available on the adjustable version of the MIC5156.
Output Regulation
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.
Out-of-Regulation Detection
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.
Current Limiting
Super LDO Regulators perform constant-current limiting (not
foldback). To implement current limiting, a sense resistor
(RS) must be placed in the “power” path between VDD and
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
Standard N-channel enhancement-mode MOSFETs are ac-
ceptable for most Super LDO regulator applications.
Logic-level N-channel enhancement-mode MOSFETs may
be necessary if the external gate drive voltage is too low
(MIC5156), or the input voltage is too low, to provide adequate
charge pump voltage (MIC5157/8) to enhance a standard
MOSFET.
Circuit Layout
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).
GND
S
G
MIC515x
V
IN
Figure 1a. Connections for Fixed Output
OUT 1.235 August 2005 9 MIC5156/5157/5158
August 2005 9 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
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).
1)
R1 = 1 × 1 04( - 1)
VO U T
1.235
GND
S
EA*
MIC5157/8
R1
R2
10k
VOUT
G
Figure 2. Typical Resistive Divider
Input Filter Capacitor
The Super LDO requires an input bypass capacitor for accom-
modating wide changes in load current and for decoupling
the error amplifier and charge pump. A medium to large value
low-ESR (equivalent series resistance) capacitor is best,
mounted close to the device.
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
aluminum electrolytic capacitors perform nicely; very low-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.
For a given step increase in load current, the output voltage will
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.
Some linear regulators specify a minimum required output filter
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.
GND
S
EA
MIC5157
or
MIC5158
G
VIN
Figure 1b. Connections for Adjustable Output
GND
MIC5156
G
VIN
EA
* Optional 16V zener diode
recommended in applications
whereVG is greater than 18V
*
Figure 1c. MIC5156 Connections for
Adjustable Output
MOSFET Gate-to-Source Protection
When using the adjustable version of the MIC5156, an external
16V zener diode placed from gate-to-source is recommended
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.
The MIC5157 operates at 3.3V when the 3.3V pin is connected
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 5V FB pin is connected to EA.
Gale Supp‘y v T 35mV <§>
MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 10 August 2005
Current Limiting
Current sensing requires a low-value series resistance (Rs)
between VDD and D (drain). Refer to the typical applications.
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.
2)
RS = 3 5 m V
IL I M
where:
RS = sense resistor value
ILIM = maximum output current
Most current-limited applications require low-value resistors.
See Application Hints 21 and 25 for construction hints.
Non-Current-Limited Applications
For circuits not requiring current limiting, do not use a sense
resistor between VDD and D (drain). See figure (3). The con-
troller will not limit current when it does not detect a 35mV
drop from VDD to D.
S
G
MIC5156
D
VDD
VIN
Figure 3. No Current Limit
3.3V Microprocessor Applications
For computer designs that use 3.3V microprocessors with 5V
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.
SMPS Post Regulator Application
A Super LDO regulator can be used as a post regulator for a
switch-mode power supply. The Super LDO regulator can pro-
vide a significant reduction in peak-to-peak ripple voltage.
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.
G
MIC5156-x.x
D
V
DD
V
IN
V
G
Gate Supply
Enable
Shutdown
EN
GND
R
S
S
Figure 4a. High-Side Switch
If a MIC5157 or MIC5158 is used and is shutdown for a
given time, the charge pump reservoir VCP will bleed off. If
recharging the reservoir causes an unacceptable delay in the
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).
GND
S
EA
MIC5158
G
EN
Output Off
Output On
1N4148
V
IN
V
DD
Figure 4b. Fast High-Side Switch
Battery Charger Application
The MIC5158 may be used in constant-current applications
such as battery chargers. See figure (5). The regulator supplies
a constant-current (35mV ÷ R3) until the battery approaches
the float voltage:
VF L = 1 . 2 3 5 (1 + )
R1
R2
where:
VFL = float voltage
At float voltage, the MOSFET is shut off. A trickle charge is
supplied by R4.
«NJ _L 47 \ 1—H— \ LA 0: i—o August 2005 11 MIC5156/5157/5158
August 2005 11 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
GND
S
EA
MIC5158
G
EN
VIN
R1
R2
D
R3 R 4
VDD
Figure 5. Battery Charger Concept
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.
Line
Battery
S
G
MIC5158
D
VDD
EN
GND
EA
1N4148
Uninterruptable
DC
D
S
D
G
S
G
MOSFET bod y diodes
shown for clarity
Off-line
Power Supply
AC
Line
Q1
Q2
40V max.
Figure 6. UPS Power Supply Concept
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MIC5156/5157/5158 Micrel, Inc.
MIC5156/5157/5158 12 August 2005
Package Information
0.380 (9.65)
0.370 (9.40) 0.135 (3.43)
0.125 (3.18)
PIN 1
DIMENSIONS:
INCH (MM)
0.018 (0.57)
0.100 (2.54)
0.013 (0.330)
0.010 (0.254)
0.300 (7.62)
0.255 (6.48)
0.245 (6.22)
0.380 (9.65)
0.320 (8.13)
0.0375 (0.952)
0.130 (3.30)
8-Pin DIP (N)
8-Pin SOIC (M)
4i 4i + V_H_H_H_H_H_H_‘ / V \_H_H_H_H_H_H_l ALW éfirWWW; 150 405 4—1 L110 2794 H¢ 023 5342 0501524 , ¢ HHHHHHH‘ V 4 HHHHHHH +LA H Mk L + fmi . u 344 a 75 , u 057 145 U 337 (8 55) u 049 (1 25) 310 7374 0 MAX 54 030 0] 52¢ ‘ § ‘7 ms 0351 g\ 4 JEEEEV, 20) , 0 22315 30 L 0 244 (s W J ’+ S & 4 August 2005 13 M|05156l5157l5158
August 2005 13 MIC5156/5157/5158
MIC5156/5157/5158 Micrel, Inc.
.080 (1.524)
.015 (0.381)
.023 (.5842)
.015 (.3810)
.310 (7.874)
.280 (7.112)
.770 (19.558) MAX
.235 (5.969)
.215 (5.461)
.060 (1.524)
.045 (1.143)
.160 MAX
(4.064)
.160 (4.064)
.100 (2.540) .110 (2.794)
.090 (2.296) .400 (10.180)
.330 (8.362)
.015 (0.381)
.008 (0.2032)
.060 (1.524)
.045 (1.143)
PIN 1
14-Pin DIP (N)
45
3–6
0.244 (6.20)
0.228 (5.80)
0.344 (8.75)
0.337 (8.55)
0.006 (0.15)
SEATING
PLANE
0.026 (0.65)
MAX)0.016 (0.40)
TYP
0.154 (3.90)
0.057 (1.45)
0.049 (1.25)
0.193 (4.90)
0.050 (1.27)
TYP
PIN 1
DIMENSIONS:
INCHES (MM)
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.