MIC5234
Low-Quiescent Current
150mA LDO Regulator
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
General Description
The MIC5234 is a low-quiescent current, Cap low-
dropout regulator. With a maximum operating input voltage
of 30V and quiescent current of 20A, it is ideal for
supplying keep-alive power in systems with high-voltage
batteries.
Capable of 150mA output, the MIC5234 has a dropout
voltage of only 320mV. It can also survive an input
transient of –20V to +32V. The MIC5234 requires only a
2.2F output capacitor for stable operation.
The MIC5234 includes a logic compatible enable input.
Other features of the MIC5234 include thermal shutdown,
current limit, overvoltage shutdown, load dump protection,
reverse-leakage and reverse battery protection.
The MIC5234 is available in an 8-pin ePad SOIC package
with a junction operating range from –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
Ultra-low quiescent current (IQ = 20A @ IO = 100A)
Wide input voltage range: 2.3V to 30V
Low dropout:
230mV @50mA
320mV @150mA
Adjustable output voltage
Typical ±1.0% initial output accuracy
Logic compatible enable input
Overcurrent protection
Thermal-shutdown protection
Reverse-leakage and reverse-battery protection
Thermally enhanced 8-pin ePad SOIC package
Applications
“Keep-alive” supply in notebook and portable personal
computers
Logic supply from high-voltage batteries
Automotive electronics
Battery-powered systems
_________________________________________________________________________________________________________________________
Typical Application
Regulator with Adjustable Output
September 2011 M9999-092711-B
hbwhelp@micrel.com
or (408) 955-1690
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Ordering Information
Part Number Voltage Junction Temperature Range Package(1) Lead Fi nish
MIC5234YME Adjustable –40°C to +125°C 8-Pin ePad SOIC NiPdAu
Note:
1. ePad SOIC is a Green RoHS-compliant package. Mold compound is halogen free.
Pin Configur ation
8-Pin ePad SOIC
Pin Description
Pin Number Pin Name Pin Function
1 VOUT Regulated Output.
2, 3, 6 NC No Connect.
4 ADJ Adjustable Feedback Input. Connect to voltage divider network.
5 EN Enable (Input). Logic low = shutdown; logic high = enabled. Do not leave floating.
7 GND Ground.
8 VIN Power Supply Input.
EP ePad Exposed Thermal Pad. Connect to the ground plane to maximize thermal performance.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN)....................................... 20V to +32V
Power Dissipation(3)...................................Internally Limited
Junction Temperature (TJ) ....................................... +150°C
Storage Temperature (TS)......................... 65°C to +150°C
Lead Temperature (soldering, 10s)............................ 260°C
ESD Rating(4) ................................................ ESD Sensitive
Operating Ratings(2)
Supply Voltage (VIN)...................................... +2.3V to +30V
Enable Voltage (VEN).......................................... 0V to +30V
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
ePad SOIC (θJA) ................................................41°C/W
Electrical Characteristics(5)
VIN = VOUT + 1V; VEN = 2.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C TJ +125°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
VADJ Feedback Voltage 1.2054 1.23 1.2546 V
ΔVOUT/ΔT Output Voltage
Temperature Coefficient(6) 50 ppm/°C
ΔVOUT/VOUT Line Regulation VIN = VOUT + 1V to 30V 0.2 0.5 %
0.15 0.3
IOUT = 100µA to 50mA(7) 0.5
0.3 0.6
ΔVOUT/VOUT Load Regulation
IOUT = 100µA to 150mA(7) 1.0
%
IOUT = 100µA 50 120
IOUT = 50mA 230 400
IOUT = 100mA 270
ΔV Dropout Voltage(8)
IOUT = 150mA 320 550
mV
VEN = 2.0V, IOUT = 100µA 20 30 µA
VEN = 2.0V, IOUT = 50mA 0.5 0.9
VEN = 2.0V, IOUT = 100mA 1.5
IGND Ground Pin Current
VEN = 2.0V, IOUT = 150mA 2.8 5.0
mA
IGND(SHDN) Ground Pin in Shutdown VEN = 0V, VIN = 30V 0.1 1 µA
ISC Short-Circuit Current VOUT = 0V 150 260 400 mA
eN Output Noise 10Hz to 100kHz, VOUT = 3.0V, COUT = 2.2µF 160 µVRMS
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(MAX) = (TJ(MAX) TA) ÷ θJA. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
5. Specification for packaged parts only.
6. Output voltage temperature coefficient is defined as the worst-case voltage change divided by the total temperature range.
7. Regulation is measured at constant junction temperature using pulse testing with a low duty cycle. Changes in output voltage due to heating effects
are covered by the speculation for thermal regulation.
8. Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value measured at
VIN=VOUT+1V.
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Electrical Characteristics(4) (Continued)
VIN = VOUT + 1V; VEN = 2.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C TJ +125°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
Enable Input
VIL Input Low Voltage Regulator off 0.6 V
VIH Input High Voltage Regulator on 2.0 V
0.01 1.0
VEN = 0.6V, regulator off 2.0
0.15 1.0
VEN = 2.0V, regulator on 2.0
0.5 2.5
IEN Enable Input Current
VEN = 30V, regulator on 5.0
µA
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Typical Characteristics
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Typical Characteristics (Continued)
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Functional Characteristics
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Functional Diagram
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Application Information
The MIC5234 is a µcap low dropout linear regulator
which provides wide input voltage range, reversed-
battery protection, reduced quiescent current and small
package. When disabled, the quiescent current is
reduced to 0.1A.
Enable
A low on the enable pin disables the part, forcing the
quiescent current to less than 0.1A. Thermal shutdown
is not functional while the device is disabled. The
maximum enable bias current is 2A for a 2.0V input. An
open collector pull-up resistor tied to the input voltage
should be set low enough to maintain 2V on the enable
input. Figure 1 shows an open collector output driving
the enable pin through a 200k pull-up resistor tied to the
input voltage. In order to avoid output oscillations, slow
transitions from low to high should be avoided.
Figure 1. Remote Enable
Input Capacitor
An input capacitor may be required when the device is
not near the source power supply or when supplied by a
battery. Small, surface mount, ceramic capacitors can be
used for bypassing. Larger values may be required if the
source supply has high ripple.
Output Capacitor
The MIC5234 has been designed to minimize the effect
of the output capacitor ESR on the closed loop stability.
As a result, ceramic or film capacitors can be used at the
output. Figure 2 displays a range of ESR values for a
10F capacitor. A 10F capacitor with an ESR less than
3.4 is sufficient for stability over the entire input voltage
range. Stability can also be maintained throughout the
specified load and line conditions with 2.2F film or
ceramic capacitors.
Figure 2. Output Capacitor ESR
Reverse Current Pro tection
The MIC5234 is designed to limit the reverse current
flow from output to input in the event that the MIC5234
output has been tied to the output of another power
supply. Refer to the Typical Characteristics to see the
graphs detailing the reverse current flow with the input
grounded and open.
Thermal Shutdown
The MIC5234 has integrated thermal protection. This
feature is only for protection purposes. The device
should never be intentionally operated near this
temperature as this may have detrimental effects on the
life of the device. The thermal shutdown may become
inactive while the enable input is transitioning a high to a
low. When disabling the device via the enable pin,
transition from a high to low quickly. This will insure that
the output remains disabled in the event of a thermal
shutdown.
ePad SOIC-8 Thermal Characteristics
The MIC5234 is a high input voltage device intended to
provide 150mA of continuous output current in one a
small profile package. The ePad SOIC-8 allows the
device to dissipate approximately 50% more power than
the SOIC-8 package.
The benefit of the MIC5234 ePad SOIC-8 package is an
improvement to less than half the thermal resistance
over the standard SO-8 packing. Lower thermal
resistance means more output current or higher input
voltage for a given package size. Lower thermal
resistance is achieved by joining the die with the die
attach paddle to create a single piece electrical and
thermal conductor. This concept has been used by
MOSFET manufacturers for years, proving very reliable
and cost effective for the user. Thermal resistance
consists of two main elements, JC (junction-to-case
thermal resistance) and CA (case-to-ambient thermal
resistance). See Figure 3. JC is the resistance from the
die to the case (ePad) of the package. CA is the
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resistance from the case (ePad) to the ambient air and it
includes CS case (ePad)-to-sink thermal resistance and
SA sink-to-ambient thermal resistance. Power dissipation in a linear regulator is calculated as
follows:
PD = (VIN – VOUT) × IOUT + (VIN × IGND)
If we use a 3V output device and a 8V input with an
output current of 150mA, then our power dissipation is
as follows:
PD = (8V – 3V) × 150mA + (8V × 2.6mA)
PD = 750mW + 20.8mW
PD = 770.8mW
A copper plane should be provided to dissipate the heat
to keep junction temperature 125°C.
Adjustable Regulator Application
Figure 3. Thermal Resistan ce The MIC5234 can be adjusted from 1.24V to 20V by
using two external resistors (see Figure 4). The resistors
set the output voltage based on Equation 1:
Using the ePad SOIC-8 reduces the JC dramatically and
allows the user to reduce CA. The total thermal
resistance, JA (junction-to-ambient thermal resistance)
is the limiting factor in calculating the maximum power
dissipation capability of the device. Typically, the ePad
SOIC-8 has a JC of 14.7°C/W, this is significantly lower
than the standard SOIC-8 which is typically 48.8°C/W.
CA is reduced because ePad can now be soldered
directly to a ground plane which significantly reduces the
case-to-sink thermal resistance and sink-to-ambient
thermal resistance.
+×= R2
R1
1VV REFOUT Eq. 1
Where VREF = 1.23V.
Low-dropout linear regulators from Micrel are rated to a
maximum junction temperature of 125°C. It is important
not to exceed this maximum junction temperature during
operation of the device. To prevent this maximum
junction temperature from being exceeded, the
appropriate ground plane heat sink must be used.
The maximum allowable temperature rise must be
calculated to determine the required heat sink:
Figure 4. Adjustable Voltage Application
T = TJ(MAX) – TA(MAX)
TJ(MAX) = 125°C Example:
TA(MAX) = maximum ambient operating temperature If output voltage to be set is 3.3V and R2 is selected as
1.2k.
Then
×= 1
V
V
2RR1
REF
OUT
For example, the maximum ambient temperature is
50°C, the T is determined as follows:
×= 1
1.23V
3.3V
k2.1R1 = 2.019 k
T = 125°C – 50°C
T = 75°C
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Evaluation Board Schematic
Bill of Materials
Item Part Number Manufacturer DESCRIPTION Qty.
C1, C5 EKY-500ELL101MHB5D United Chemi-con(1) Capacitor, Aluminum, 100µF, 50V, 20%, Radial 2
12065C475KAT2A AVX(2)
GRM31CR71H475KA12L Murata(3)
C2, C3
C3216X5R1H475K TDK(4)
Capacitor, 4.7µF, 50V, X5R, size 1206 2
0805YD225KAT2A AVX(2)
GRM219R61C225KA88D Murata(3)
C4
C2012X7R1C225K TDK(4)
Capacitor, 2.2µF, 16V, X7R, size 0805 1
R1 CRCW060310K0FKEA Vishay (5) Resistor, 10K, 1%, size 0603 1
R2 CRCW06031200FKEA Vishay (5) Resistor, 120, 1%, size 0603 1
R3 CRCW06033830FKEA Vishay (5) Resistor, 383, 1%, size 0603 1
R4 CRCW06032000FKEA Vishay (5) Resistor, 200, 1%, size 0603 1
R5 CRCW06031270FKEA Vishay (5) Resistor, 127, 1%, size 0603 1
R6 CRCW060356R0FKEA Vishay (5) Resistor, 56, 1%, size 0603 1
U1 MIC5234YME Micrel(6) Low-Quiescent Current µCap LDO Regulator 1
Notes:
1. United Chemi-Con: www.chemi-con.com.
2. AVX: www.avx.com.
3. Murata: www.murata.com.
4. TDK: www.tdk.com.
5. Vishay: www.vishay.com.
6. Micrel, Inc.: www.micrel.com.
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PCB Layout Recommendations
MIC5234 Evaluation Board Top Layer
MIC5234 Evaluation Bo ard Bottom Layer
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PCB Layout Recommendations (Continued)
MIC5234 Evaluation Board Top Silk
MIC5234 Evaluation Bo ard Botto m Silk
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Package Information
8-Pin ePad SOIC (NE)
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Recommended Land Pattern
8-Pin ePad SOIC (NE)
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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
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