Page 1
MIC29310/29312 Micrel
MIC29310/29312
3A Fast-Response LDO Regulator
General Description
The MIC29310 and MIC29312 are low cost versions of
MIC29300 family low-dropout (LDO) regulators. Manufactured 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 transient recovery from input voltage surges and output load
current changes.
The MIC29310 is available in fixed 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.
For applications requiring even lower dropout
voltage, input voltage greater than 16V, or an
error flag, see the MIC29300/29301/29302/
29303.
Ordering Information
Part Number Voltage Junction Temp. Range Package
MIC29310-3.3BT 3.3V 0°C to +125°C TO-220-3
MIC29310-3.3BU 3.3V 0°C to +125°C TO-263-3
MIC29310-5.0BT 5.0V 0°C to +125°C TO-220-3
MIC29310-5.0BU 5.0V 0°C to +125°C TO-263-3
MIC29312BT Adj. 0°C to +125°C TO-220-5
MIC29312BU Adj. 0°C to +125°C TO-263-5
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-efficiency “green” computer systems
• High-efficiency linear power supplies
• High-efficiency switching supply post regulator
• Battery-powered equipment
Typical Application
MIC29312
On
Off
V
V
IN
IN OUT
GND
V
OUT
IN
* For best performance, total series resistance
(R1 + R2) should be small enough to pass
the minimum regulator load current of 10mA.
Fixed Regulator Configuration
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
EN
IN
V
OUT
Adjustable Regulator Configuration
GND
= 1.240
OUT
ADJ
R1
R2
R1*
R2*
+ 1
July 1999 1 MIC29310/29312
V
OUT
Page 2
MIC29310/29312 Micrel
Pin Configuration
TAB
TAB
MIC29310-x.xBT
TO-220 (T)
MIC29312-x.xBT
TO-220-5 (T)
3 OUT
2 GND
1IN
5 ADJ
4 OUT
3 GND
2IN
1EN
TAB
MIC29310-x.xBU
TO-263 (U)
TAB
MIC29312-x.xBU
TO-263-5 (U)
3 OUT
2 GND
1IN
5 ADJ
4 OUT
3 GND
2IN
1EN
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.
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
MIC29310/29312 2 July 1999
Page 3
MIC29310/29312 Micrel
Electrical Characteristics
TJ = 25°C, bold values indicate 0°C ≤ TJ ≤ +125°C; unless noted
Parameter Condition Min Typ Max Units
Output Voltage 10mA ≤ IO ≤ IFL, (V
Line Regulation IO = 10mA, (V
Load Regulation VIN = V
OUT
+ 1V, 10mA ≤ I
OUT
∆VO / ∆T Output VoltageTemperature Coefficient, Note 8 20 100 ppm/°C
Dropout Voltage ∆V
= –1%, Note 5
OUT
Ground Current I
Ground Pin VIN = 0.5V less than specified V
I
GNDDO
Current at Dropout
Current Limit V
= 0V, Note 6 3.0 3.8 A
OUT
Minimum Load Current 710mA
e
, Output Noise Voltage CL = 10µF400µV
n
(10Hz to 100kHz) IL = 100mA CL = 33µF260µV
Reference (MIC29312 only)
Reference Voltage 10mA ≤ IO ≤ IFL, V
Adjust Pin Bias Current 40 80 nA
Reference Voltage Note 9 20 ppm/°C
Temperature Coefficient
Adjust Pin Bias Current 0.1 nA/°C
Temperature Coefficient
Enable Input (MIC29312 only)
Input Logic Voltage low (off) 0.8 V
high (on) 2.4 V
Enable Pin Input Current V
= V
EN
IN
V
= 0.8V – 2 µA
EN
Regulator Output Note 10 10 µA
Current in Shutdown 20 µA
+ 1V) ≤ VIN ≤ 8V, Note 4 –2 2 %
OUT
+ 1V) ≤ VIN ≤ 16V 0.06 0.5 %
≤ I
OUT
FULL LOAD
= 100mA 80 200 mV
I
O
= 750mA 220 mV
I
O
I
= 1.5A 330 mV
O
, Notes 4, 8 0.2 1 %
IO = 3A 600 1000 mV
= 750mA, VIN = V
O
I
= 1.5A 15 mA
O
+ 1V 5 20 mA
OUT
IO = 3A 60 150 mA
. I
OUT
+ 1V ≤ VIN ≤ 8V, Note 4 1.215 1.265 V
OUT
= 10mA 2 3 mA
OUT
MAX
120 nA
15 30 µA
75 µA
4 µA
RMS
RMS
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 defined as 3A for the MIC29310/29312. For testing, V
Note 5: Dropout voltage is defined as the input-to-output differential when the output voltage drops to 99% of its nominal value with V
Note 6: For this test, VIN is the larger of 8V or V
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
Note 8: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 9: V
Note 10: VEN ≤ 0.8V and VIN ≤ 8V, V
to VIN.
pin current.
≤ V
REF
+ 3V.
OUT
≤ (VIN – 1V), 2.4V ≤ VIN ≤ 16V, 10mA < IL ≤ IFL, TJ ≤ T
OUT
OUT
= 0.
J(max).
is programmed to 5V.
OUT
+ 1V applied
OUT
July 1999 3 MIC29310/29312
Page 4
MIC29310/29312 Micrel
Block Diagram
IN
*EN
On/Off
Thermal
Shutdown
Bias
Reference
16V
* MIC29312 only.MIC29310/29312
O.V.
I
LIMIT
Feed-
back
OUT
ADJ*
GND
MIC29310/29312 4 July 1999
Page 5
MIC29310/29312 Micrel
0
0.2
0.4
0.6
0.8
1
-60 -30 0 30 60 90 120 150
DROPOUT VOLTAGE (mV)
TEMPERATURE (°C)
Typical Characteristics
MIC29312 Load Transient Response
(See Test Circuit Schematic)
V
OUT
3.525V nominal
4 × 330µF
AVX
TPSE337M006R0100
tantalum
+20mV
3.525V
–20mV
1ms/division
VIN = V
OUT
+ 1V
MIC29312
EN
IN
GND
V
load (not shown):
OUT
OUT
ADJ
0.1µF
93.1k
1%
49.9k
1%
Intel® Power Validator
MIC29312 Load Transient Response Test Circuit
MIC29312 Line Transient Response
with 3A Load, 10µF Output Capacitance
6.525V
4.525V
200µs/division
= 3A
I
OUT
C
=10µF
+20mV
3.525V
OUT
3A
LOAD CURRENT OUTPUT VOLTAGE
200mA
0mA
MIC29312 Line Transient Response
with 3A Load, 100µF Output Capacitance
6.525V
4.525V
+20mV
3.525V
200µs/division
= 3A
I
OUT
C
= 100µF
OUT
–20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC2931x Dropout Voltage
0.60
0.50
0.40
July 1999 5 MIC29310/29312
0.30
0.20
0.10
DROPOUT VOLTAGE (V)
0.00
0123
vs. Output Current
OUTPUT CURRENT (A)
–20mV
OUTPUT VOLTAGE INPUT VOLTAGE
MIC2931x Dropout Voltage
vs. Temperature
I
= 3A
LOAD
MIC29310-3.3
Dropout Characteristics
5.0
4.0
I
= 10mA
LOAD
3.0
2.0
1.0
OUTPUT VOLTAGE (V)
0.0
0246
I
= 3A
LOAD
INPUT VOLTAGE (V)
Page 6
MIC29310/29312 Micrel
MIC2931x Ground Current
2.0
1.5
1.0
0.5
GROUND CURRENT (mA)
0.0
vs. Input Voltage
I
= 10mA
OUT
0246810
INPUT VOLTAGE (V)
MIC2931x Ground Current
6.0
5.0
4.0
3.0
2.0
1.0
GROUND CURRENT (mA)
0.0
vs. Temperature
I
= 750mA
OUT
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
MIC2931x Ground Current
200
150
100
GROUND CURRENT (mA)
vs. Input Voltage
I
= 3A
OUT
50
0
0246810
INPUT VOLTAGE (V)
MIC2931x Ground Current
vs. Temperature
20
15
I
10
5
GROUND CURRENT (mA)
0
-60 -30 0 30 60 90 120 150
= 1.5A
OUT
TEMPERATURE (°C)
MIC2931x Ground Current
vs. Input Voltage
2.0
V
1.5
1.0
0.5
0.0
GROUND CURRENT (mA)
-0.5
= 3.3V
OUT
R
= 100Ω
LOAD
-20 -10 0 10 20
INPUT VOLTAGE (V)
MIC2931x Ground Current
100
GROUND CURRENT (mA)
vs. Temperature
80
60
40
20
0
-60 -30 0 30 60 90 120 150
I
= 3A
OUT
TEMPERATURE (°C)
MIC2931x Ground Current
vs. Output Current
60
50
40
30
20
10
GROUND CURRENT (mA)
0
0123
OUTPUT CURRENT (A)
MIC29312 Enable Current
40
35
30
25
20
15
10
ENABLE CURRENT (µA)
vs. Temperaure
VEN = 5V
VEN = 2V
5
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
MIC29310-3.3 Output Voltage
3.40
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
OUTPUT VOLTAGE (V)
3.22
3.20
vs. Temperature
3 DEVICES
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
MIC29312 Adjust Pin Current
vs. Temperature
50
40
30
20
10
ADJUST PIN CURRENT (nA)
0
-60 -30 0 30 60 90 120 150
I
= 10mA
LOAD
TEMPERATURE (°C)
MIC2931x Short Circuit
Current vs. Temperature
6
5
4
3
2
CURRENT (A)
1
0
-60 -30 0 30 60 90 120 150
V
= 0V
OUT
TEMPERATURE (°C)
MIC2931x Output Impedance
10
1
0.1
0.01
OUTPUT IMPEDANCE (Ω)
0.001
vs. Frequency
0
0
10x10
100x10
FREQUENCY (Hz)
3
1x10
3
10x10
3
100x10
6
1x10
MIC29310/29312 6 July 1999
Page 7
MIC29310/29312 Micrel
Applications Information
The MIC29310 and MIC29312 are high performance lowdropout voltage regulators suitable for all moderate to highcurrent voltage regulator applications. Their 600mV of dropout voltage at full load make them especially valuable in
battery powered systems and as high efficiency noise filters
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
voltages in excess of the desired output voltage to be applied
without reverse current flow. 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 highcurrent Super ßeta PNP™ regulators have identical pinouts.
V
IN
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-specific
parameters:
• Maximum ambient temperature, T
• Output Current, I
• Output Voltage, V
• Input Voltage, V
OUT
OUT
IN
A
First, we calculate the power dissipation of the regulator from
these numbers and the device parameters from this datasheet.
PD = I
Where the ground current is approximated by 2% of I
Then the heat sink thermal resistance is determined with this
formula:
θSA = —————— – (θJC + θCS)
Where T
≤ 125°C and θCS is between 0 and 2°C/W.
J MAX
The heat sink may be significantly reduced in applications
where the minimum input voltage is known and is large
compared 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
significant 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
examples on thermal design and heat sink specification.
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 capacitors 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
supplies 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 tolerances are considered.
Minimum Load Current
The MIC29310/2 regulators are specified between finite
× (1.02VIN – V
OUT
T
– T
J MAX
P
D
)
OUT
OUT
A
.
July 1999 7 MIC29310/29312
Page 8
MIC29310/29312 Micrel
loads. If the output current is too small, leakage currents
dominate and the output voltage rises. A 10mA minimum
load current is necessary for proper regulation.
Adjustable Regulator Design
MIC29312BT
V
IN
4.75V to 5.25V
10µF
R1
100k
R2
56.2k
V
= 1.240V × [1 + (R1 / R2)]
OUT
22µF
V
OUT
3.45V
Figure 4. Adjustable Regulator with Resistors
The adjustable regulator version, MIC29312, allows programming 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 definition. 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 allows
“zero” current drain when the device is disabled—only microamperes of leakage current flows. 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.
Resistor Value Table for the MIC29312 Adjustable Regulator
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
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).
MIC29310/29312 8 July 1999
Page 9
MIC29310/29312 Micrel
Package Information
0.151 D ±0.005
0.108 ±0.005
(2.74 ±0.13)
0.818 ±0.005
(20.78 ±0.13)
(3.84 D ±0.13)
0.410 ±0.010
(10.41 ±0.25)
0.356 ±0.005
(9.04 ±0.13)
0.176 ±0.005
(4.47 ±0.13)
0.590 ±0.005
(14.99 ±0.13)
0.050 ±0.005
(1.27 ±0.13)
7°
0.050 ±0.003
(1.27 ±.08)
0.100 ±0.005
(2.54 ±0.13)
0.108 ±0.005
(2.74 ±0.13)
0.400 ±0.015
(10.16 ±0.38)
0.030 ±0.003
(0.76 ±0.08)
TO-220-3 (T)
0.150 D ±0.005
(3.81 D ±0.13)
0.241 ±0.017
(6.12 ±0.43)
0.578 ±0.018
(14.68 ±0.46)
1.140 ±0.010
(28.96 ±0.25)
0.018 ±0.008
(0.46 ±0.020)
7°
3°
0.100 ±0.020
DIMENSIONS:
0.177 ±0.008
(4.50 ±0.20)
0.050 ±0.005
(1.27 ±0.13)
SEATING
PLANE
(2.54 ±0.51)
INCH
(MM)
7°
Typ.
0.550 ±0.010
(13.97 ±0.25)
0.067 ±0.005
(1.70 ±0.127)
0.268 REF
(6.81 REF)
0.032 ±0.005
(0.81 ±0.13)
0.018 ±0.008
(0.46 ±0.20)
Dimensions:
0.103 ±0.013
(2.62±0.33)
inch
(mm)
TO-220-5 (T)
July 1999 9 MIC29310/29312
Page 10
MIC29310/29312 Micrel
0.405±0.005
0.065±0.010
20°±2°
0.100 BSC 0.050
DIM. = INCH
0.405±0.005
0.065±0.010
20°±2°
0.050±0.005
0.360±0.005
0.600±0.025
TO-263-3 (U)
0.050±0.005
0.360±0.005
0.600±0.025
8° MAX
0.015 ±0.002
0.176±0.005
0.050±0.005
SEATING PLANE
+0.004
0.004
–0.008
0.100±0.01
0.176±0.005
0.060±0.005
0.067±0.005 0.032 ±0.003
DIM. = INCH
TO-263-5 (U)
8° MAX
0.015 ±0.002
SEATING PLANE
+0.004
0.004
–0.008
0.100±0.01
MIC29310/29312 10 July 1999
Page 11
MIC29310/29312 Micrel
July 1999 11 MIC29310/29312
Page 12
MIC29310/29312 Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 1999 Micrel Incorporated
MIC29310/29312 12 July 1999
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