MIC5231
Micrel
MIC5231
Micropower
µ
Cap LDO Regulator
Preliminary Information
General Description
The MIC5231
µCap
low-dropout voltage regulator is intended
for low-output-current biasing applications. It features ex-
tremely low ground current, not greater than 4µA under all
load and temperature conditions, making it efficient and ideal
for keep-alive applications in devices such as notebook
computers.
The MIC5231 offers better than 2% initial accuracy and low
dropout (typically 150mV at 10mA output current). An output
capacitor is not required for stable operation, decreasing cost
and board space. Tiny ceramic chip capacitors may be used
to improve transient response.
The MIC5231 also features a control pin which allows the
regulator to be shut down when not required. Its shutdown-
state draws zero current, benefitting battery-powered appli-
cations.
The MIC5231 is available in fixed output voltages of 2.75V,
3.0V, 3.3V and 5V in the small SOT-23-5 IttyBitty™ package.
Contact Micrel for other voltage options.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Extremely low quiescent current—
only 0.65
µ
A
No output capacitor requirement
Stable with ceramic or tantalum capacitors
IttyBitty™ SOT-23-5 surface-mount package
10mA output drive
Low 150mV at 10mA dropout voltage
Tight load and line regulation
Low temperature coefficient
Logic-level enable input
Real time clocks
SRAM backup
Cellular telephones
Laptop, notebook and palmtop computers
Battery-powered equipment
Bar code scanners
SMPS post-regulator and dc-to-dc modules
Applications
Ordering Information
Part Number
MIC5231-2.75BM5
MIC5231-3.0BM5
MIC5231-3.3BM5
MIC5231-5.0BM5
Marking
LM2H
LM30
LM33
LM50
Voltage
2.75V
3.0V
3.3V
5.0V
Temperature Range
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Package
SOT-23-5
SOT-23-5
SOT-23-5
SOT-23-5
Typical Application
MIC5231-5.0BM5
V
IN
6V
IN
EN
GND
OUT
V
OUT
5V
5V Linear Regulator Application
IttyBitty is a trademark of Micrel, Inc.
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970
June 2000
1
MIC5231
MIC5231
Micrel
Pin Configuration
IN GND EN
3
2
1
LM50
4
5
Part
Identification
OUT
NC
MIC5231-5.0BM5
Pin Description
Pin Number
1
2
3
4
5
Pin Name
EN
GND
IN
OUT
NC
Pin Function
Enable (Input): Active high. Logic high = enable; logic low = shutdown. Do
not float.
Ground
Supply Input
Regulated Output
not internally connected
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
IN
) .................................... –0.6V to +14V
Lead Temperature (soldering, 5 sec.) ....................... 260°C
Storage Temperature (T
A
) ....................... –60°C to +150°C
ESD,
Note 3
.................................................................. 2kV
Operating Ratings
(Note 2)
Input Voltage (V
IN
) ........................................... 3.5V to 12V
Ambient Temperature (T
A
) ......................... –40°C to +85°C
Junction Temperature (T
J
) ....................... –40°C to +125°C
Thermal Resistance,
Note 4
MIC5231
2
June 2000
MIC5231
Micrel
Electrical Characteristics
V
IN
= V
OUT
+ 1V; I
L
= 100µA; C
L
= 0.47µF; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤
+125°C; unless noted.
Symbol
V
OUT
∆V
OUT
/∆T
∆V
OUT
/V
OUT
∆V
OUT
/V
OUT
V
DO
I
Q
PSRR
Enable Input
V
ENL
I
ENL
I
ENH
Note 1.
Note 2.
Note 3.
Note 4:
Note 5:
Note 6:
Note 7:
Parameter
Output Voltage Accuracy
Output Voltage
Temperature Coefficient
Line Regulation
Load Regulation
Dropout Voltage,
Note 7
Conditions
variation from nominal V
OUT
Note 5
V
IN
= 6V to 12V
I
L
= 10µA to 10mA,
Note 6
I
L
= 1mA
I
L
= 10mA
V
IN
= 6V, I
L
= 10mA
V
IN
= 12V, I
L
= 10mA
f = 100Hz, I
L
= 100µA
V
EN
= logic low (regulator off)
V
EN
= logic high ((regulator on)
Min
–2
–3
Typ
Max
+2
+3
Units
%
%
ppm/°C
250
0.2
0.2
15
150
0.65
1.1
50
300
3
4
0.25
1
%
%
mV
mV
µA
µA
dB
Ground Pin Current
Ripple Rejection
Enable Input Voltage
0.4
1.4
1
1
0.18
V
V
nA
nA
Enable Input Current
Enable Input Current
V
ENL
≤
0.18V (regulator off)
V
ENH
≥
1.4V (regulator on)
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended.
The maximum allowable power dissipation at any T
A
(ambient temperature) is P
D(max)
= (T
J(max)
– T
A
)
÷ θ
JA
. The
θ
JC
of the MIC5231 is
130°C/W. Mounted to a standard PC board, the
θ
JA
is approximately 235°C/W.
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Regulation is measured at constant junction temperature using low duty cycle pulse testing.
Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V
differential. For outputs below 3.5V, dropout voltage is the input-to-output differential with the minimum input voltage 3.5V. Minimum input
operating voltage is 3.5V.
June 2000
3
MIC5231
MIC5231
Micrel
Ground Current
vs. Output Current
1
GROUND CURRENT (µA)
Ground Current (µA)
0.8
0.7
0.6
0.5
0.4
0.3
0
0
1
10
OUTPUT CURRENT (mA)
0.2
2
Ground Current
vs. Supply Voltage
1
GROUND CURRENT (µA)
0.8
0.6
0.4
0.2
0
-40
Ground Current
vs. Temperature
0.5
4
6
8
10
Supply Voltage (V)
12
0
40
80
TEMPERATURE (°C)
120
Ground Current
vs. Temperature
SHORT CIRCUIT CURRENT (mA)
3.10
OUTPUT VOLTAGE (V)
150
Short Circuit Current
vs. Temperature
3.05
100
3.00
50
2.95
2.90
-50
-20 10 40 70 100 130
TEMPERATURE (°C)
0
-50
-20 10 40 70 100 130
TEMPERATURE (°C)
MIC5231
4
June 2000
MIC5231
Micrel
Block Diagram
IN
OUT
EN
Bandgap
Reference
MIC5231
GND
Applications Information
Input Capacitor
A 0.1µF (or larger) capacitor should be placed from the IN
(supply input) to GND (ground) if there is more than 20 cm of
wire between IN and the ac filter capacitor or if supplied from
a battery.
Output Capacitors
The MIC5231 does not require an output capacitor for stabil-
ity. A 1µF or larger capacitor is recommended between OUT
(output) and GND to improve the regulator’s transient re-
sponse. A 0.1µF capacitor can be used to reduce overshoot
recovery time at the expense of overshoot amplitude. The
ESR (effective series resistance) of this capacitor has no
effect on regulator stability, but low-ESR capacitors improve
high frequency transient response. The value of this capaci-
tor may be increased without limit, but values larger than
10µF tend to increase the settling time after a step change in
input voltage or output current.
The MIC5231 has no minimum load current; it will remain
stable and in regulation with no load (other than the internal
voltage divider). This is especially important in real-time clock
and CMOS RAM keep-alive applications.
Minimum Load Current
The MIC5231 does not require a minimum load for proper
operation. This allows the device to operate in applications
where very light output currents are required for keep-alive
purposes. This is important for powering SRAM or Flash
memory in low-power modes for handheld devices.
Safe Operating Conditions
The MIC5231 does not incorporate current limit or thermal
shutdown in the design. The output pass element is approxi-
mately 15 ohms, therefore, when a short occurs from the
output to ground, the current is self-limited. The pass element
has a positive temperature coefficient, such that when the
device gets hot, the output impedance goes up, limiting the
current even further. The maximum junction temperature for
the device is 125°C, and it is important that this is not
exceeded for any length of time.
Thermal Considerations
The MIC5231 is not intended for sourcing currents that would
cause a large power loss in the device, but since it is not
current limited, it is possible to source more than the rated
10mA. At this point, it is important to ensure that the die
temperature does not exceed 125°C.
Power dissipation in the regulator is calculated as follows:
P
D
= (V
IN
– V
OUT
)*I
OUT
+ V
IN
*I
GND
The MIC5231 consumes only 0.65uA over load and does not
need to consider that contribution in the power dissipation
equation, therefore the equation is simplified.
P
D
= (V
IN
– V
OUT
)*I
OUT
The MIC5231, in the IttyBitty SOT23-5 package, has a
thermal resistance, junction-to-ambient, of 235°C/W. Using
this number, the power dissipation capability of that package,
without exceeding a 125°C junction temperature rating, can
easily be calculated.
P
D(max)
= (T
j(max)
– Ta)/θ
JA
P
D(max)
= (125°C – Ta)/235°C/W
If the device is being operated at 85°C, the maximum power
June 2000
5
MIC5231
嵌入式系统
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