November 2006 1 MIC29310/29312
MIC29310/29312 Micrel
General Description
The MIC29310 and MIC29312 are low cost versions of
MIC29300 family low-dropout (LDO) regulators. Manufac-
tured on Micrel’s proprietary Super beta PNP™ process,
the MIC29310/2 is a 3A LDO regulator with very low-dropout
voltage (600mV over the full load) and low ground current.
Along with a total accuracy of ±2% (over temperature, line
and load regulation) these regulators feature very fast tran-
sient recovery from input voltage surges and output load
current changes.
The MIC29310 is available in fi xed 3.3V and 5V outputs
voltages; the MIC29312 has an adjustable output which can
be set by two external resistors to a voltage between 1.24V
to 15V. In addition, all versions are fully protected against
overcurrent faults, reversed input polarity, reversed lead
insertion, and overtemperature operation.
A TTL logic enable (EN) pin is available in the MIC29312 to
shutdown the regulator. When not used, the device can be set
to continuous operation by connecting EN to the input (IN).
The MIC29310/2 is available in the standard 3- and 5-pin
TO-220 and TO-263 packages with an operating junction
temperature range of 0°C to +125°C.
Features
• Low cost versions of MIC29300 family
• Fast transient response
• 3A current over full temperature range
• 600mV dropout voltage at full load
• Low ground current
• Accurate 1% guaranteed tolerance
• “Zero” current shutdown mode (MIC29312)
• Fixed voltage and adjustable versions
Applications
• Processor peripheral and I/O supplies
• PC add-in cards
• High-effi ciency “green” computer systems
• High-effi ciency linear power supplies
• High-effi ciency switching supply post regulator
• Battery-powered equipment
MIC29310/29312
3A Fast-Response LDO Regulator
Typical Application
IN OUT
GND
VIN VOUT
MIC29310-x.x
Fixed Regulator Confi guration
MIC29312
OUT
ADJ R1* VOUT
* For best performance, total series resistance
(R1 + R2) should be small enough to pass
the minimum regulator load current of 10mA.
R2*
EN
GND
VIN IN
On
Off
VOUT = 1.240 R1
R2+ 1
Adjustable Regulator Confi guration
For applications requiring even lower dropout
voltage, input voltage greater than 16V, or an
error fl ag, see the MIC29300/29301/29302/
29303.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC29310/29312 Micrel
MIC29310/29312 2 November 2006
Pin Description
Pin Number Pin Number Pin Name Pin Function
MIC29310 MIC29312
1 EN Enable (Input): Active-high, logic-level enable/shutdown control.
1 2 IN Unregulated Input: +16V maximum supply.
2,
TAB 3, TAB GND Ground: Ground pin and TAB are internally connected.
3 4 OUT Regulator Output
5 ADJ Ouput Voltage Adjust: 1.24V feedback from external resistive divider.
Pin Confi guration
TAB
3OUT
2GND
1IN
MIC29310-x.xBT/WT
TO-220-3 (T)
TAB
5ADJ
4OUT
3GND
2IN
1EN
MIC29312-x.xBT/WT
TO-220-5 (T)
TAB
3OUT
2GND
1IN
MIC29310-x.xBU/WU
TO-263-3 (U)
TAB
5ADJ
4OUT
3GND
2IN
1EN
MIC29312-x.xBU/WU
TO-263-5 (U)
Absolute Maximum Ratings (Note 1)
Input Voltage (VIN) ..........................................–20V to +20V
Power Dissipation (PD) ............................. Internally Limited
Storage Temperature Range (TS) ............. –65°C to +150°C
Lead Temperature (soldering, 5 sec.) ........................ 260°C
ESD, Note 3
Operating Ratings (Note 2)
Input Voltage (VIN) ........................................ +2.3V to +16V
Junction Temperature (TJ) ............................ 0°C to +125°C
Package Thermal Resistance
TO-263 (θJC) ......................................................... 2°C/W
TO-220 (θJC) ......................................................... 2°C/W
TO-220 (θJA) ....................................................... 55°C/W
Ordering Information
Part Number Voltage Junction Temperature
Range Package
Standard RoHS Compliant(1)
MIC29310-3.3BT MIC29310-3.3WT 3.3V 0°C to +125°C TO-220
MIC29310-3.3BU MIC29310-3.3WU 3.3V 0°C to +125°C TO-263
MIC29310-5.0BT MIC29310-5.0WT 5.0V 0°C to +125°C TO-220
MIC29310-5.0BU MIC29310-5.0WU 5.0V 0°C to +125°C TO-263
MIC29312BT MIC29312WT Adj. 0°C to +125°C TO-220
MIC29312BU MIC29312WU Adj. 0°C to +125°C TO-263
Note:
1. RoHS compliant with “high-melting solder” exemption.
November 2006 3 MIC29310/29312
MIC29310/29312 Micrel
Electrical Characteristics(Note 11)
TJ = 25°C, bold values indicate 0°C ≤ TJ ≤ +125°C; unless noted
Parameter Condition Min Typ Max Units
Output Voltage 10mA ≤ IO ≤ IFL, (VOUT + 1V) ≤ VIN ≤ 8V, Note 4 –2 2 %
Line Regulation IO = 10mA, (VOUT + 1V) ≤ VIN ≤ 16V 0.06 0.5 %
Load Regulation VIN = VOUT + 1V, 10mA ≤ IOUT ≤ IFULL LOAD, Notes 4, 8 0.2 1 %
ΔVO / ΔT Output Voltage Temperature Coeffi cient, Note 8 20 100
ppm/°C
Dropout Voltage ΔVOUT = –1%, Note 5
I
O = 100mA 80 200 mV
I
O = 750mA 220 mV
I
O = 1.5A 330 mV
I
O = 3A 600 1000 mV
Ground Current IO = 750mA, VIN = VOUT + 1V 5 20 mA
I
O = 1.5A 15 mA
I
O = 3A 60 150 mA
IGNDDO Ground Pin VIN = 0.5V less than specifi ed VOUT. IOUT = 10mA 2 3 mA
Current at Dropout
Current Limit VOUT = 0V, Note 6 3.0 3.8 A
Minimum Load Current 7 10 mA
en, Output Noise Voltage CL = 10µF 400 µVRMS
(10Hz to 100kHz) IL = 100mA CL = 33µF 260 µVRMS
Reference (MIC29312 only)
Reference Voltage 10mA ≤ IO ≤ IFL, VOUT + 1V ≤ VIN ≤ 8V, Note 4 1.215 1.265 V
MAX
Adjust Pin Bias Current 40 80 nA
120 nA
Reference Voltage Note 9 20
ppm/°C Temperature Coeffi cient
Adjust Pin Bias Current 0.1 nA/°C
Temperature Coeffi cient
Enable Input (MIC29312 only)
Input Logic Voltage low (off) 0.8 V
high (on) 2.4 V
Enable Pin Input Current VEN = VIN 15 30 µA
75 µA
V
EN = 0.8V – 2 µA
4 µA
Regulator Output Note 10 10 µA
Current in Shutdown 20 µA
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: Full Load current is defi ned as 3A for the MIC29310/29312. For testing, VOUT is programmed to 5V.
Note 5: Dropout voltage is defi ned as the input-to-output differential when the output voltage drops to 99% of its nominal value with VOUT + 1V applied
to VIN.
Note 6: For this test, VIN is the larger of 8V or VOUT + 3V.
Note 7: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground
pin current.
Note 8: Output voltage temperature coeffi cient is defi ned as the worst case voltage change divided by the total temperature range.
Note 9: V
REF ≤ VOUT ≤ (VIN – 1V), 2.4V ≤ VIN ≤ 16V, 10mA < IL ≤ IFL, TJ ≤ TJ(max).
Note 10: V
EN ≤ 0.8V and VIN ≤ 8V, VOUT = 0.
Note 11: Specifi cation for packaged product only.
MIC29310/29312 Micrel
MIC29310/29312 4 November 2006
Block Diagram
On/Off
Reference
Bias
Feed-
back
GND
16V
OUT
ADJ*
*EN
IN
O.V.
ILIMIT
Thermal
Shut-
down
* MIC29312 only.MIC29310/29312
November 2006 5 MIC29310/29312
MIC29310/29312 Micrel
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0123
DROPOUT VOLTAGE (V)
OUTPUT CURRENT (A)
MIC2931x Dropout Voltage
vs. Output Current
0
0.2
0.4
0.6
0.8
1
-60 -30 0 30 60 90 120 150
DROPOUT VOLTAGE (mV)
TEMPERATURE (°C)
MIC2931x Dropout Voltage
vs. Temperature
I
LOAD
= 3A
0.0
1.0
2.0
3.0
4.0
5.0
0246
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
MIC29310-3.3
Dropout Characteristics
I
LOAD
= 3A
I
LOAD
= 10mA
Typical Characteristics
6.525V
4.525V
3.525V
+20mV
–20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC29312 Line Transient Response
with 3A Load, 100F Output Capacitance
200s/division
I
OUT
= 3A
C
OUT
= 100F
6.525V
4.525V
3.525V
+20mV
–20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC29312 Line Transient Response
with 3A Load, 10F Output Capacitance
200s/division
I
OUT
= 3A
C
OUT
=10F
0mA
200mA
3A
3.525V
+20mV
–20mV
LOAD CURRENT OUTPUT VOLTAGE
MIC29312 Load Transient Response
(See Test Circuit Schematic)
1ms/division
V
IN
= V
OUT
+ 1V
MIC29312
EN
IN
OUT
ADJ
GND
0.1µF 93.1k
1%
49.9k
1%
V
OUT
3.525V nominal
4 × 330µF
AVX
TPSE337M006R0100
tantalum
V
OUT
load (not shown): Intel® Power Validator
MIC29312 Load Transient Response Test Circuit
MIC29310/29312 Micrel
MIC29310/29312 6 November 2006
0
10
20
30
40
50
-60 -30 0 30 60 90 120 150
ADJUST PIN CURRENT (nA)
TEMPERATURE ( °C)
MIC29312 Adjust Pin Current
vs. Temperature
ILOAD = 10mA
0.0
1.0
2.0
3.0
4.0
5.0
6.0
-60 -30 0 30 60 90 120 150
GROUND CURRENT (mA)
TEMPERATURE (°C)
MIC2931x Ground Current
vs. Temperature
I
OUT
= 750mA
0
5
10
15
20
-60 -30 0 30 60 90 120 150
GROUND CURRENT (mA)
TEMPERATURE (°C)
MIC2931x Ground Current
vs. Temperature
I
OUT
= 1.5A
0
20
40
60
80
100
-60 -30 0 30 60 90 120 150
GROUND CURRENT (mA)
TEMPERATURE (°C)
MIC2931x Ground Current
vs. Temperature
I
OUT
= 3A
0
10
20
30
40
50
60
0123
GROUND CURRENT (mA)
OUTPUT CURRENT (A)
MIC2931x Ground Current
vs. Output Current
3.20
3.22
3.24
3.26
3.28
3.30
3.32
3.34
3.36
3.38
3.40
-60 -30 0 30 60 90 120 150
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
MIC29310-3.3 Output Voltage
vs. Temperature
3 DEVICES
0
1
2
3
4
5
6
-60 -30 0 30 60 90 120 150
CURRENT (A)
TEMPERATURE (°C)
MIC2931x Short Circuit
Current vs. Temperature
VOUT = 0V
0
5
10
15
20
25
30
35
40
-60 -30 0 30 60 90 120 150
ENABLE CURRENT (µA)
TEMPERATURE (°C)
MIC29312 Enable Current
vs. Temperaure
VEN = 5V
VEN = 2V
0.001
0.01
0.1
1
10
10x100
100x100
1x103
10x103
100x103
1x106
OUTPUT IMPEDANCE (Ω)
FREQUENCY (Hz)
MIC2931x Output Impedance
vs. Frequency
0.0
0.5
1.0
1.5
2.0
0246810
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
MIC2931x Ground Current
vs. Input Voltage
I
OUT
= 10mA
0
50
100
150
200
0246810
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
MIC2931x Ground Current
vs. Input Voltage
I
OUT
= 3A
-0.5
0.0
0.5
1.0
1.5
2.0
-20 -10 0 10 20
GROUND CURRENT (mA)
INPUT VOLTAGE (V)
MIC2931x Ground Current
vs. Input Voltage
RLOAD = 100Ω
VOUT = 3.3V
November 2006 7 MIC29310/29312
MIC29310/29312 Micrel
Applications Information
The MIC29310 and MIC29312 are high performance low-drop-
out voltage regulators suitable for all moderate to high-current
voltage regulator applications. Their 600mV of dropout voltage
at full load make them especially valuable in battery powered
systems and as high effi ciency noise fi lters in “post-regulator”
applications. Unlike older NPN-pass transistor designs, where
the minimum dropout voltage is limited by the base-emitter
voltage drop and collector-emitter saturation voltage, dropout
performance of the PNP output of these devices is limited
merely by the low VCE saturation voltage.
A trade-off for the low dropout voltage is a varying base
drive requirement. But Micrel’s Super ßeta PNP™ process
reduces this drive requirement to merely 2% to 5% of the
load current.
MIC29310/312 regulators are fully protected from damage
due to fault conditions. Current limiting is provided. This
limiting is linear; output current under overload conditions
is constant. Thermal shutdown disables the device when
the die temperature exceeds the maximum safe operating
temperature. Transient protection allows device (and load)
survival even when the input voltage spike above and below
nominal. The output structure of these regulators allows volt-
ages in excess of the desired output voltage to be applied
without reverse current fl ow. The MIC29312 version offers a
logic level ON/OFF control: when disabled, the devices draw
nearly zero current.
An additional feature of this regulator family is a common
pinout: a design’s current requirement may change up or down
yet use the same board layout, as all of Micrel’s high-current
Super ßeta PNP™ regulators have identical pinouts.
IN OUT
GND
V
OUT
Figure 3. The MIC29310 regulator requires only two
capacitors for operation.
Thermal Design
Linear regulators are simple to use. The most complicated
design parameters to consider are thermal characteristics.
Thermal design requires the following application-specifi c
parameters:
• Maximum ambient temperature, TA
• Output Current, IOUT
• Output Voltage, VOUT
• Input Voltage, VIN
First, we calculate the power dissipation of the regulator
from these numbers and the device parameters from this
datasheet.
PD = IOUT × (1.02VIN – VOUT)
Where the ground current is approximated by 2% of IOUT.
Then the heat sink thermal resistance is determined with
this formula:
T
J MAX – TA
θSA = —————— – (θJC + θCS)
P
D
Where TJ MAX ≤ 125°C and θCS is between 0 and 2°C/W.
The heat sink may be signifi cantly reduced in applications
where the minimum input voltage is known and is large com-
pared with the dropout voltage. Use a series input resistor to
drop excessive voltage and distribute the heat between this
resistor and the regulator. The low dropout properties of Micrel
Super ßeta PNP regulators allow very signifi cant reductions
in regulator power dissipation and the associated heat sink
without compromising performance. When this technique is
employed, a capacitor of at least 0.1µF is needed directly
between the input and regulator ground.
Please refer to Application Note 9 for further details and ex-
amples on thermal design and heat sink specifi cation.
Capacitor Requirements
For stability and minimum output noise, a capacitor on the
regulator output is necessary. The value of this capacitor
is dependent upon the output current; lower currents allow
smaller capacitors. MIC29310/2 regulators are stable with a
minimum capacitor value of 10µF at full load.
This capacitor need not be an expensive low ESR type:
aluminum electrolytics are adequate. In fact, extremely low
ESR capacitors may contribute to instability. Tantalum capaci-
tors are recommended for systems where fast load transient
response is important.
Where the regulator is powered from a source with a high
AC impedance, a 0.1µF capacitor connected between Input
and GND is recommended. This capacitor should have good
characteristics to above 250kHz.
Transient Response and 5V to 3.3V Conversion
The MIC29310/2 have excellent response to variations in
input voltage and load current. By virtue of their low dropout
voltage, these devices do not saturate into dropout as readily
as similar NPN-based designs. A 3.3V output Micrel LDO will
maintain full speed and performance with an input supply as
low as 4.2V, and will still provide some regulation with sup-
plies down to 3.8V, unlike NPN devices that require 5.1V
or more for good performance and become nothing more
than a resistor under 4.6V of input. Micrel’s PNP regulators
provide superior performance in “5V to 3.3V” conversion
applications than NPN regulators, especially when all toler-
ances are considered.
Minimum Load Current
The MIC29310/2 regulators are specifi ed between fi nite loads.
If the output current is too small, leakage currents dominate
MIC29310/29312 Micrel
MIC29310/29312 8 November 2006
and the output voltage rises. A 10mA minimum load current
is necessary for proper regulation.
Adjustable Regulator Design
Figure 4. Adjustable Regulator with Resistors
The adjustable regulator version, MIC29312, allows program-
ming the output voltage anywhere between 1.25V and the
15V maximum operating rating of the family. Two resistors
are used. Resistors can be quite large, up to 1MΩ, because
of the very high input impedance and low bias current of the
sense comparator. The resistor values are calculated by:
V
OUT
R1 = R2 × ( –—— – 1 )
1.240
Where VO is the desired output voltage. Figure 4 shows
component defi nition. Applications with widely varying load
currents may scale the resistors to draw the minimum load
current required for proper operation (see the table below).
Enable Input
The MIC29312 version features an enable (EN) input that
allows ON/OFF control of the device. Special design al-
lows “zero” current drain when the device is disabled—only
microamperes of leakage current fl ows. The EN input has
TTL/CMOS compatible thresholds for simple interfacing with
logic, or may be directly tied to VIN. Enabling the regulator
requires approximately 20µA of current into the EN pin.
Voltage Standard (Ω) Min. Load (Ω)
R1 R2 R1 R2
2.85 100k 76.8k 162 124
2.9 100k 75.0k 165 124
3.0 100k 69.8k 174 124
3.1 100k 66.5k 187 124
3.15 100k 64.9k 191 124
3.3 100k 60.4k 205 124
3.45 100k 56.2k 221 124
3.6 100k 52.3k 237 124
3.8 100k 48.7k 255 124
4.0 100k 45.3k 274 124
4.1 100k 43.2k 287 124
Resistor Value Table for the MIC29312 Adjustable Regulator
Note: This regulator has a minimum load requirement. “Standard” values assume the load meets this requirement. “Minimum
Load” values are calculated to draw 10mA and allow regulation with an open load (the minimum current drawn from the load
may be zero).
November 2006 9 MIC29310/29312
MIC29310/29312 Micrel
Package Information
3-Pin TO-220 (T)
3-Pin TO-263 (U)
MIC29310/29312 Micrel
MIC29310/29312 10 November 2006
5-Pin TO-220 (T)
5-Pin TO-263 (U)
November 2006 11 MIC29310/29312
MIC29310/29312 Micrel
MIC29310/29312 Micrel
MIC29310/29312 12 November 2006
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
The 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 specifi cations at any time without notifi cation 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 signifi cant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Incorporated.
