July 2009 Doc ID 8188 Rev 7 1/17
17
LD2982BXX18
Very low drop and low noise voltage regulator with
inhibit function, low ESR capacitors compatible
Features
■Very low dropout voltage (120 mV at 50 mA
and 7 mV at 1 mA load)
■Very low quiescent current (375 mA typ. at
50 mA load and 75 mA at 1 mA)
■Output current up to 50 mA
■Logic controlled electronic shutdown
■Output voltage of 1.8 V
■Internal current and thermal limit
■Available in ± 1 % tolerance
(at 25 °C, A version)
■Supply voltage rejection: 45 dB (typ)
■Only 1 µF for stability
■Low output noise voltage 30 µVrms
■Smallest package SOT23-5L
■Temperature range: -40 °C to 125 °C
Description
The LD2982 is a 50 mA fixed output voltage
regulator. The ultra low drop voltage and the low
quiescent current make them particularly suitable
for low noise, low power applications, and in
battery powered systems. In sleep mode
quiescent current is less than 1 µA when INHIBIT
pin is pulled low. Shutdown logic control function
is available on pin 3 (TTL compatible). This
means that when the device is used as local
regulator, it is possible to put a part of the board in
standby, decreasing the total power consumption.
An external capacitor CBYP = 10 nF connected
between bypass pin and GND reduce the noise to
30 µVrms.
Typical application are in cellular phone,
palmtop/laptop computer, personal digital
assistant (PDA), personal stereo, camcorder and
camera.
SOT23-5L
Table 1. Device summary
Order code Output voltage
LD2982BM18R 1.8 V
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Contents LD2982BXX18
2/17 Doc ID 8188 Rev 7
Contents
1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 External capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2 Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3 Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.4 Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5 Inhibit input operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.6 Reverse current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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LD2982BXX18 Diagram
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1 Diagram
Figure 1. Schematic diagram
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Pin configuration LD2982BXX18
4/17 Doc ID 8188 Rev 7
2 Pin configuration
Figure 2. Pin connections (top view)
Table 2. Pin description
Pin n° Symbol Name and function
1 IN Input port
2 GND Ground pin
3 INHIBIT Control switch ON/OFF. Inhibit is not internally pulled-up; it cannot be left floating.
Disable the device when connected to GND or to a positive voltage less than 0.18V
4 Bypass Bypass Pin: Capacitor to be connected to GND in order to improve the thermal noise
performances
5 OUT Output port
Table 3. Thermal data
Symbol Parameter SOT23-5L Unit
RthJC Thermal resistance junction-case 81 °C/W
RthJA Thermal resistance junction-ambient 255 °C/W
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LD2982BXX18 Maximum ratings
Doc ID 8188 Rev 7 5/17
3 Maximum ratings
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
Table 4. Absolute maximum ratings
Symbol Parameter Value Unit
VIDC input voltage 16 V
VINH INHIBIT input voltage 16 V
IOOutput current Internally limited
PDPower dissipation Internally limited
TSTG Storage temperature range -65 to 150 °C
TOP Operating junction temperature range -40 to 125 °C
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Electrical characteristics LD2982BXX18
6/17 Doc ID 8188 Rev 7
4 Electrical characteristics
TJ = 25 °C, VI = VO + 1 V, IO = 1 mA, VSHDN = 2 V, CI = CO = 1 µF, unless otherwise
specified.
Table 5. Electrical characteristics for LD2982BXX18
Symbol Parameter Test conditions Min. Typ. Max. Unit
VOP Operating input voltage 2.5 16 V
VOOutput voltage
VI = 2.5V 1.477 1.5 1.523
VIO = 1 to 50mA 1.470 1.530
IO = 1 to 50mA, TJ= -40 to 125°C 1.447 1.553
VOOutput voltage
VI = 2.8V 1.773 1.8 1.827
VIO = 1 to 50mA 1.764 1.836
IO = 1 to 50mA, TJ= -40 to 125°C 1.737 1.863
VOOutput voltage
VI = 3.5V 2.462 2.5 2.537
VIO = 1 to 50mA 2.45 2.55
IO = 1 to 50mA, TJ= -40 to 125°C 2.412 2.587
VOOutput voltage
VI = 3.8V 2.758 2.8 2.842
VIO = 1 to 50mA 2.744 2.856
IO = 1 to 50mA, TJ= -40 to 125°C 2.702 2.898
VOOutput voltage
VI = 3.85V 2.807 2.85 2.893
VIO = 1 to 50mA 2.793 2.907
IO = 1 to 50mA, TJ= -40 to 125°C 2.750 2.950
VOOutput voltage
VI = 4.0V 2.955 3.0 3.045
VIO = 1 to 50mA 2.94 3.06
IO = 1 to 50mA, TJ= -40 to 125°C 2.895 3.105
VOOutput voltage
VI = 4.1V 3.053 3.1 3.146
VIO = 1 to 50mA 3.038 3.162
IO = 1 to 50mA, TJ= -40 to 125°C 2.991 3.208
VOOutput voltage
VI = 4.2V 3.152 3.2 3.248
VIO = 1 to 50mA 3.136 3.264
IO = 1 to 50mA, TJ= -40 to 125°C 3.088 3.312
VOOutput voltage
VI = 4.3V 3.250 3.3 3.349
VIO = 1 to 50mA 3.234 3.366
IO = 1 to 50mA, TJ= -40 to 125°C 3.184 3.415
VOOutput voltage
VI = 4.5V 3.447 3.5 3.552
VIO = 1 to 50mA 3.430 3.370
IO = 1 to 50mA, TJ= -40 to 125°C 3.377 3.662
VOOutput voltage
VI = 4.6V 3.546 3.6 3.654
VIO = 1 to 50mA 3.528 3.672
IO = 1 to 50mA, TJ= -40 to 125°C 3.474 3.726
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LD2982BXX18 Electrical characteristics
Doc ID 8188 Rev 7 7/17
VOOutput voltage
VI = 4.8V 3.743 3.8 3.857
VIO = 1 to 50mA 3.724 3.876
IO = 1 to 50mA, TJ= -40 to 125°C 3.667 3.933
VOOutput voltage
VI = 5.0V 3.94 4 4.06
VIO = 1 to 50mA 3.92 4.08
IO = 1 to 50mA, TJ= -40 to 125°C 3.86 4.14
VOOutput voltage
VI = 5.7V 4.629 4.7 4.77
VIO = 1 to 50mA 4.606 4.794
IO = 1 to 50mA, TJ= -40 to 125°C 4.535 4.864
VOOutput voltage
VI = 6.0V 4.925 5 5.075
VIO = 1 to 50mA 4.9 5.1
IO = 1 to 100 mA, TJ= -40 to 125°C 4.825 5.175
ISC Short circuit current RL = 0 400 mA
ΔVO/ΔVILine regulation
VI = VO + 1V to 16V, IO = 1 mA 0.003 0.014
%/VI
VI = VO + 1V to 16V, IO = 1 mA,
TJ= -40 to 125°C 0.032
VDROP Dropout voltage
IO = 0 1 3
mV
IO = 0, TJ= -40 to 125°C 5
IO = 1mA 7 10
IO = 1mA, TJ= -40 to 125°C 15
IO = 10mA 40 60
IO = 10mA, TJ= -40 to 125°C 90
IO = 50mA 120 150
IO = 50mA, TJ= -40 to 125°C 225
IQ
Quiescent current
ON MODE
IO = 0 80 100
µA
IO = 0, TJ= -40 to 125°C 150
IO = 1mA 100 150
IO = 1mA, TJ= -40 to 125°C 200
IO = 10mA 200 300
IO = 10mA, TJ= -40 to 125°C 400
IO = 50mA 600 900
IO = 50mA, TJ= -40 to 125°C 1200
OFF MODE VINH<0.18V 0
VINH<0.18V, TJ= -40 to 125°C 1
SVR Supply voltage rejection CBYP = 0.01µF, CO = 10µF, f = 1kHz 45 dB
VIL Inhibit input logic low TJ= -40 to 125°C 0.15 V
VIH Inhibit input logic high TJ= -40 to 125°C 2 V
IINH Inhibit input current VINH = 0V, TJ= -40 to 125°C 5 15 µA
VINH = 5V, TJ= -40 to 125°C 0 -1
eNOutput noise voltage B = 300 Hz to 50 kHz, CBYP = 0.01µF,
CO = 10µF 30 µV
Table 5. Electrical characteristics for LD2982BXX18 (continued)
Symbol Parameter Test conditions Min. Typ. Max. Unit
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Typical characteristics LD2982BXX18
8/17 Doc ID 8188 Rev 7
5 Typical characteristics
(TJ = 25 °C, VI = VO(NOM) +1 V, CI = 1 µF (X7R), CO = 2.2 µF (X7R), VINH = 2 V, unless
otherwise specified).
Figure 3. Output voltage vs. temperature Figure 4. Dropout voltage vs. temperature
Figure 5. Dropout voltage vs. output current Figure 6. Quiescent current vs. load current
Figure 7. Quiescent current vs. temperature Figure 8. Supply voltage rejection vs. temp.
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LD2982BXX18 Typical characteristics
Doc ID 8188 Rev 7 9/17
Figure 9. Supply voltage rejection vs. output
current
Figure 10. Supply voltage rejection vs. output
current
Figure 11. Supply voltage rejection vs.
frequency
Figure 12. Supply voltage rejection vs.
frequency
Figure 13. Line transient Figure 14. Line transient
VO = 2.5V, IO = 50mA, no CI, CO = 4.7µF, tr=tf=2ns
VO = 2.5V, IO = 50mA, no CI, CO = 4.7µF, tr=tf=1µs
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Typical characteristics LD2982BXX18
10/17 Doc ID 8188 Rev 7
Figure 15. Load transient Figure 16. Load transient
VO = 2.5V, IO = 0 to 50mA, no CI, CO = 10µF, tr=tf=2ns
VO = 2.5V, IO = 0 to 50mA, no CI, CO = 4.7µF, tr=tf=2ns
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LD2982BXX18 Application notes
Doc ID 8188 Rev 7 11/17
6 Application notes
6.1 External capacitors
Like any low-dropout regulator, the LD2982 requires external capacitors for regulator
stability. This capacitor must be selected to meet the requirements of minimum capacitance
and equivalent series resistance. We suggest to solder input and output capacitors as close
as possible to the relative pins.
6.2 Input capacitor
An input capacitor whose value is 1 µF is required with the LD2982 (amount of capacitance
can be increased without limit). This capacitor must be located a distance of not more than
0.5" from the input pin of the device and returned to a clean analog ground. Any good quality
ceramic, tantalum or film capacitors can be used for this capacitor.
6.3 Output capacitor
The LD2982 is designed specifically to work with ceramic output capacitors. It may also be
possible to use tantalum capacitors, but these are not as attractive for reasons of size and
cost. By the way, the output capacitor must meet both the requirement for minimum amount
of capacitance and ESR (equivalent series resistance) value. Due to the different loop gain,
the stability improves for higher output versions and so the suggested minimum output
capacitor value, if low ESR ceramic type is used, is 1 µF for output voltages equal or major
than 3.8 V, 2.2 µF for VO going from 1.8 to 3.3 V, and 3.3 µF for the other versions. However,
if an output capacitor lower than the suggested one is used, it's possible to make stable the
regulator adding a resistor in series to the capacitor.
6.4 Important
The output capacitor must maintain its ESR in the stable region over the full operating
temperature to assure stability. Also, capacitor tolerance and variation with temperature
must be considered to assure the minimum amount of capacitance is provided at all times.
This capacitor should be located not more than 0.5" from the output pin of the device and
returned to a clean analog ground.
6.5 Inhibit input operation
The inhibit pin can be used to turn OFF the regulator when pulled low, so drastically
reducing the current consumption down to less than 1 µA. When the inhibit feature is not
used, this pin must be tied to VI to keep the regulator output ON at all times. To assure
proper operation, the signal source used to drive the inhibit pin must be able to swing above
and below the specified thresholds listed in the electrical characteristics section under VIH
VIL. Any slew rate can be used to drive the inhibit.
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Application notes LD2982BXX18
12/17 Doc ID 8188 Rev 7
6.6 Reverse current
The power transistor used in the LD2982 has not an inherent diode connected between the
regulator input and output. If the output is forced above the input, no current will flow from
the output to the input across the series pass transistor. When a VREV voltage is applied on
the output, the reverse current measured flows to the GND across the two feedback
resistors. This current typical value is 160 µA. R1 and R2 resistors are implanted type;
typical values are, respectively, 42.6 kΩ and 51.150 kΩ.
Figure 17. Reverse current test circuit
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LD2982BXX18 Package mechanical data
Doc ID 8188 Rev 7 13/17
7 Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
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Package mechanical data LD2982BXX18
14/17 Doc ID 8188 Rev 7
Dim.
mm. mils.
Min. Typ. Max. Min. Typ. Max.
A0.90 1.45 35.4 57.1
A1 0.00 0.10 0.0 3.9
A2 0.90 1.3035.4 51.2
b0.35 0.50 13.7 19.7
C0.090.20 3.5 7.8
D2.803.00 110.2 118.1
E 1.50 1.75 59.0 68.8
e0.9537.4
H 2.60 3.00 102.3118.1
L 0.10 0.60 3.923.6
SOT23-5L mechanical data
7049676D
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LD2982BXX18 Package mechanical data
Doc ID 8188 Rev 7 15/17
Dim.
mm. inch.
Min. Typ. Max. Min. Typ. Max.
A180 7.086
C 12.813.0 13.2 0.504 0.512 0.519
D 20.2 0.795
N60 2.362
T 14.4 0.567
Ao 3.133.233.33 0.1230.127 0.131
Bo 3.07 3.17 3.27 0.120 0.124 0.128
Ko 1.27 1.37 1.47 0.050 0.054 0.0.58
Po 3.94.0 4.1 0.1530.157 0.161
P3.94.0 4.1 0.1530.157 0.161
Tape & reel SOT23-xL mechanical data
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Revision history LD2982BXX18
16/17 Doc ID 8188 Rev 7
8 Revision history
Table 6. Document revision history
Date Revision Changes
25-Jul-2006 4 Order codes updated.
14-Feb-2008 5 Added: Table 1 on page 1.
10-Jul-2008 6 Modified: Table 1 on page 1 and Table 5 on page 6.
29-Jul-2009 7 Modified: Table 1 on page 1.
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LD2982BXX18
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