1/17September 2003
■STABLE WITH LOW ESR CERAMIC
CAPACITORS
■ULTRA LOW DROPOUT VOLTAGE (0.17V
TYP. AT 100mA LOAD, 7mV TYP. AT 1mA
LOAD)
■VERY LOW QUIESCENT CURRENT (80µA
TYP. AT NO LOAD IN ON MODE; MAX 1µA
IN OFF MODE)
■GUARANTEED OUTPUT CURRENT UP TO
100mA
■LOGIC-CONTROLLED ELECTRONIC
SHUTDOWN
■OUTPUT VOLTAGE OF 1.5; 1.8; 2.5; 2.85;
3.0; 3.2; 3.3; 3.6; 3.8; 4.0; 4.7; 4.85; 5.0V
■INTERNAL CURRENT AND THERMAL LIMIT
■± 0.75% TOLERANCE OUTPUT VOLTAGE
AVAILABLE (A VERSION)
■OUTPUT LOW NOISE VOLTAGE 160µVRMS
■TEMPERATURE RANGE: -40 TO 125°C
■SMALLEST PACKAGE SOT23-5L AND
SOT-89
■FAST DYNAMIC RESPONSE TO LINE AND
LOAD CHANGES
DESCRIPTION
The LD2981 series are 100mA fixed-output
voltage regulator. The low drop-voltage and the
ultra low quiescent current make them suitable for
low noise, low power applications and in battery
powered systems.
The quiescent current in sleep mode is less than
1µA when INHIBIT pin is pulled low. Shutdown
Logic Control function is available on pin n.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. The LD2981 is designed to
work with low ESR ceramic capacitor. Typical
applications are in cellular phone, palmtop/laptop
computer, personal digital assistant (PDA),
personal stereo, camcorder and camera.
LD2981
SERIES
ULTRA LOW DROP VOLTAGE REGULATORS WITH INHIBIT
LOW ESR OUTPUT CAPACITORS COMPATIBLE
SCHEMATIC DIAGRAM
SOT23-5L SOT-89
LD2981 SERIES
2/17
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
THERMAL DATA
CONNECTION DIAGRAM (top view)
PIN DESCRIPTION
Symbol Parameter Value Unit
VIDC Input Voltage -0.3 to 16 V
VINH INHIBIT Input Voltage -0.3 to 16 V
IOOutput Current Internally limited
PDPower Dissipation Internally limited
TSTG Storage Temperature Range -55 to 150 °C
TOP Operating Junction Temperature Range -40 to 125 °C
Symbol Parameter SOT23-5L SOT-89 Unit
Rthj-case Thermal Resistance Junction-case 81 15 °C/W
Rthj-amb Thermal Resistance Junction-ambient 255 110 °C/W
Pin N°
SOT23-5L Pin N°
SOT-89 Symbol Name and Function
13 V
IN Input Port
2 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 NC Not Connected
51V
OUT Output Port
SOT23-5L SOT-89
LD2981 SERIES
3/17
ORDERING CODES
TYPICAL APPLICATION CIRCUIT
(*) Inhibit Pin is not internally pulled-up then it must not be left floating. Disable the device when connected to GND or to a positive voltage
less than 0.18V.
AB VERSION C VERSION OUTPUT
VOLTAGES
SOT23-5L SOT-89 SOT23-5L SOT-89
LD2981CM15TR LD2981CU15TR 1.5 V
LD2981CM18TR LD2981CU18TR 1.8 V
LD2981ABM25TR LD2981ABU25TR LD2981CM25TR LD2981CU25TR 2.5 V
LD2981ABM28TR LD2981ABU28TR LD2981CM28TR LD2981CU28TR 2.85 V
LD2981ABM30TR LD2981ABU30TR LD2981CM30TR LD2981CU30TR 3.0 V
LD2981ABM32TR LD2981ABU32TR LD2981CM32TR LD2981CU32TR 3.2 V
LD2981ABM33TR LD2981ABU33TR LD2981CM33TR LD2981CU33TR 3.3 V
LD2981ABM36TR LD2981ABU36TR LD2981CM36TR LD2981CU36TR 3.6 V
LD2981ABM38TR LD2981ABU38TR LD2981CM38TR LD2981CU38TR 3.8 V
LD2981ABM40TR LD2981ABU40TR LD2981CM40TR LD2981CU40TR 4.0 V
LD2981ABM47TR LD2981ABU47TR LD2981CM47TR LD2981CU47TR 4.7 V
LD2981ABM48TR LD2981ABU48TR LD2981CM48TR LD2981CU48TR 4.85 V
LD2981ABM50TR LD2981ABU50TR LD2981CM50TR LD2981CU50TR 5.0 V
LD2981 SERIES
4/17
ELECTRICAL CHARACTERISTICS FOR LD2981AB (Tj= 25°C, VI=V
O(NOM) +1V, CI=1µF(X7R),
CO=2.2µF(X7R), IO=1mA,V
INH = 2V, unless otherwise specified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VOP Operating Input Voltage 2.5 16 V
VOOutput Voltage IO= 1 mA 2.481 2.5 2.518 V
IO= 1 to 100 mA 2.475 2.525
IO= 1 to 100 mA TJ= -40 to 125°C 2.437 2.562
VOOutput Voltage IO= 1 mA 2.828 2.85 2.872 V
IO= 1 to 100 mA 2.822 2.878
IO= 1 to 100 mA TJ= -40 to 125°C 2.779 2.921
VOOutput Voltage IO= 1 mA 2.977 3 3.023 V
IO= 1 to 100 mA 2.970 3.030
IO= 1 to 100 mA TJ= -40 to 125°C 2.925 3.075
VOOutput Voltage IO= 1 mA 3.176 3.2 3.224 V
IO= 1 to 100 mA 3.168 3.232
IO= 1 to 100 mA TJ= -40 to 125°C 3.12 3.28
VOOutput Voltage IO= 1 mA 3.275 3.3 3.325 V
IO= 1 to 100 mA 3.267 3.333
IO= 1 to 100 mA TJ= -40 to 125°C 3.217 3.383
VOOutput Voltage IO= 1 mA 3.573 3.6 3.627 V
IO= 1 to 100 mA 3.564 3.636
IO= 1 to 100 mA TJ= -40 to 125°C 3.510 3.690
VOOutput Voltage IO= 1 mA 3.771 3.8 3.829 V
IO= 1 to 100 mA 3.762 3.838
IO= 1 to 100 mA TJ= -40 to 125°C 3.705 3.895
VOOutput Voltage IO= 1 mA 3.97 4 4.03 V
IO= 1 to 100 mA 3.96 4.04
IO= 1 to 100 mA TJ= -40 to 125°C 3.9 4.1
VOOutput Voltage IO= 1 mA 4.664 4.7 4.735 V
IO= 1 to 100 mA 4.653 4.747
IO= 1 to 100 mA TJ= -40 to 125°C 4.582 4.817
VOOutput Voltage IO= 1 mA 4.813 4.85 4.887 V
IO= 1 to 100 mA 4.801 4.899
IO= 1 to 100 mA TJ= -40 to 125°C 4.729 4.971
VOOutput Voltage IO= 1 mA 4.962 5 5.038 V
IO= 1 to 100 mA 4.950 5.050
IO= 1 to 100 mA TJ= -40 to 125°C 4.875 5.125
∆VOLine Regulation VO(NOM) +1<V
IN <16V I
O= 1 mA 0.003 0.014 %/V
TJ= -40 to 125°C 0.032
LD2981 SERIES
5/17
(NOTE 1): For Vo < 2.5V dropout voltage can be calculated according to the minimum input voltage in full temperature range.
IQQuiescent Current
ON MODE IO= 0 80 100 µA
IO=0 T
J
= -40 to 125°C 150
IO= 1 mA 100 150
IO=1mA T
J
= -40 to 125°C 200
IO= 25 mA 250 400
IO=25mA T
J
= -40 to 125°C 800
IO= 100 mA 1000 1300
IO= 100 mA TJ= -40 to 125°C 2600
OFF MODE VINH < 0.3 V 0.8
VINH < 0.15 V TJ= -40 to 125°C 2
VDROP Dropout Voltage (NOTE 1) IO=0 1 3 mV
I
O=0 T
J
= -40 to 125°C 5
IO=1mA 7 10
I
O=1mA T
J
= -40 to 125°C 15
IO= 25mA 70 100
IO= 25mA TJ= -40 to 125°C 150
IO= 100mA 180 250
IO= 100mA TJ= -40 to 125°C 375
ISC Short Circuit Current RL= 0 150 mA
SVR Supply Voltage Rejection CO=10µFf=1KHz 63 dB
V
INH Inhibit Input Logic Low LOW = Output OFF TJ= -40 to 125°C 0.18 V
VINL Inhibit Input Logic High HIGH = Output ON TJ= -40 to 125°C 1.6 V
IINH Inhibit Input Current VINH =0V T
J
= -40 to 125°C 0-1µA
V
INH =5V T
J
= -40 to 125°C 515
e
N
Output Noise Voltage BW= 300 Hz to 50 KHz CO=10µF 160 µVRMS
TSHDN Thermal Shutdown 170 °C
Symbol Parameter Test Conditions Min. Typ. Max. Unit
LD2981 SERIES
6/17
ELECTRICAL CHARACTERISTICS FOR LD2981C (Tj= 25°C, VI=V
O(NOM) +1V, CI=1µF(X7R),
CO=2.2µF(X7R), IO=1mA,V
INH = 2V, unless otherwise specified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VOP Operating Input Voltage 2.5 16 V
VOOutput Voltage IO= 1 mA 1.478 1.5 1.522 V
IO= 1 to 100 mA 1.470 1.530
IO= 1 to 100 mA TJ= -40 to 125°C 1.445 1.555
VOOutput Voltage IO= 1 mA 1.777 1.8 1.822 V
IO= 1 to 100 mA 1.764 1.836
IO= 1 to 100 mA TJ= -40 to 125°C 1.737 1.863
VOOutput Voltage IO= 1 mA 2.468 2.5 2.531 V
IO= 1 to 100 mA 2.45 2.55
IO= 1 to 100 mA TJ= -40 to 125°C 2.412 2.587
VOOutput Voltage IO= 1 mA 2.814 2.85 2.885 V
IO= 1 to 100 mA 2.793 2.907
IO= 1 to 100 mA TJ= -40 to 125°C 2.75 2.949
VOOutput Voltage IO= 1 mA 2.962 3 3.037 V
IO= 1 to 100 mA 2.94 3.06
IO= 1 to 100 mA TJ= -40 to 125°C 2.895 3.105
VOOutput Voltage IO= 1 mA 3.16 3.2 3.24 V
IO= 1 to 100 mA 3.136 3.264
IO= 1 to 100 mA TJ= -40 to 125°C 3.088 3.312
VOOutput Voltage IO= 1 mA 3.258 3.3 3.341 V
IO= 1 to 100 mA 3.234 3.366
IO= 1 to 100 mA TJ= -40 to 125°C 3.184 3.415
VOOutput Voltage IO= 1 mA 3.555 3.6 3.645 V
IO= 1 to 100 mA 3.528 3.672
IO= 1 to 100 mA TJ= -40 to 125°C 3.474 3.726
VOOutput Voltage IO= 1 mA 3.752 3.8 3.847 V
IO= 1 to 100 mA 3.724 3.876
IO= 1 to 100 mA TJ= -40 to 125°C 3.667 3.933
VOOutput Voltage IO= 1 mA 3.95 4 4.05 V
IO= 1 to 100 mA 3.92 4.08
IO= 1 to 100 mA TJ= -40 to 125°C 3.86 4.14
VOOutput Voltage IO= 1 mA 4.641 4.7 4.758 V
IO= 1 to 100 mA 4.606 4.794
IO= 1 to 100 mA TJ= -40 to 125°C 4.535 4.864
VOOutput Voltage IO= 1 mA 4.789 4.85 4.91 V
IO= 1 to 100 mA 4.753 4.947
IO= 1 to 100 mA TJ= -40 to 125°C 4.68 5.019
VOOutput Voltage IO= 1 mA 4.937 5 5.062 V
IO= 1 to 100 mA 4.9 5.1
IO= 1 to 100 mA TJ= -40 to 125°C 4.825 5.175
LD2981 SERIES
7/17
(NOTE 1): For Vo < 2.5V dropout voltage can be calculated according to the minimum input voltage in full temperature range.
∆VOLine Regulation VO(NOM) +1<V
IN <16V I
O= 1 mA 0.003 0.014 %/V
TJ= -40 to 125°C 0.032
IQQuiescent Current
ON MODE IO= 0 80 100 µA
IO=0 T
J
= -40 to 125°C 150
IO= 1 mA 100 150
IO=1mA T
J
= -40 to 125°C 200
IO= 25 mA 250 400
IO=25mA T
J
= -40 to 125°C 800
IO= 100 mA 1000 1300
IO= 100 mA TJ= -40 to 125°C 2600
OFF MODE VINH < 0.3 V 0.8
VINH < 0.15 V TJ= -40 to 125°C 2
VDROP Dropout Voltage (NOTE 1) IO=0 1 3 mV
I
O=0 T
J
= -40 to 125°C 5
IO=1mA 7 10
I
O=1mA T
J
= -40 to 125°C 15
IO= 25mA 70 100
IO= 25mA TJ= -40 to 125°C 150
IO= 100mA 180 250
IO= 100mA TJ= -40 to 125°C 375
ISC Short Circuit Current RL= 0 150 mA
SVR Supply Voltage Rejection CO=10µFf=1KHz 63 dB
V
INH Inhibit Input Logic Low LOW = Output OFF TJ= -40 to 125°C 0.18 V
VINL Inhibit Input Logic High HIGH = Output ON TJ= -40 to 125°C 1.6 V
IINH Inhibit Input Current VINH =0V T
J
= -40 to 125°C 0-1µA
V
INH =5V T
J
= -40 to 125°C 515
e
N
Output Noise Voltage BW= 300 Hz to 50 KHz CO=10µF 160 µVRMS
TSHDN Thermal Shutdown 170 °C
Symbol Parameter Test Conditions Min. Typ. Max. Unit
LD2981 SERIES
8/17
TYPICAL PERFORMANCE CHARACTERISTICS (Tj= 25°C, VI=V
O(NOM) +1V, CI=1µF(X7R),
CO=2.2µF(X7R), VINH = 2V, unless otherwise specified)
Figure 1 : Output Voltage vs Temperature
Figure 2 : Output Voltage vs Temperature
Figure 3 : Line Regulation vs Temperature
Figure 4 : Load Regulation vs Temperature
Figure 5 : Dropout Voltage vs Temperature
Figure 6 : Quiescent Current vs Temperature
LD2981 SERIES
9/17
Figure 7 : Quiescent Current vs Output
Current
Figure 8 : OFF MODE Quiescent Current vs
Temperature
Figure 9 : Quiescent Current vs Input Voltage
Figure 10 : Dropout Voltage vs Output Current
Figure 11 : Inhibit Input Current vs Temperature
Figure 12 : Inhibit Voltage vs Temperature
LD2981 SERIES
10/17
Figure 13 : Supply Voltage Rejection vs
Frequency
Figure 14 : Noise Voltage vs Frequency
Figure 15 : Best Case: Highest Output Version
Figure 16 : Worst Case: Lowest Output Version
Figure 17 : Load Transient Response
Figure 18 : Line Transient Response
V
O=
4
.7
V
,
I
O=
1
to
100
m
A
,
C
O=
4
.7µ
FX
7
R
V
I=
(V
O(NOM) +
1V)
,
V
O=
4
.7
V
,
I
O=
100
m
A
,
C
O=
4
.7µ
FX
7
R
LD2981 SERIES
11/17
APPLICATION NOTES
EXTERNAL CAPACITORS
Like any low-dropout regulator, the LD2981 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.
INPUT CAPACITOR
An input capacitor whose value is 1µF is required with the LD2981 (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 returnedto a clean analog ground. Any goodquality ceramic, tantalum or film capacitors
can be used for this capacitor.
OUTPUT CAPACITOR
The LD2981 is designedspecifically 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. The figures 1 and 2 show the allowable ESR range as a function of the output
capacitance. These curves represent the stability region over the full temperature and IOrange. 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 1µF for output voltages equal or major than
3.8V, 2.2µF for output voltages from 2.85 to 3.3V, and 3.3µF 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 (see Figure1 & Figure2 to choose the right value according to the used version
and keeping in account that the ESR of ceramic capacitors has been measured @ 100KHz).
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.
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 1µA. When the inhibit feature is not used, this pin must be tied to VIto
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.Anyslewratecanbeusedtodrivetheinhibit.
REVERSE CURRENT
The power transistorused in the LD2981 has not an inherent diode connected betweenthe 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,
according to the test circuit in figure 19, flows to the GND across the two feedback resistors. This current
typical value is 160µA. R1and R2resistors are implanted type; typical values are, respectively, 42.6 KΩ
and 51.150 KΩ.
LD2981 SERIES
12/17
Figure 19 : Reverse Current Test Circuit
LD2981 SERIES
13/17
DIM. mm. mils
MIN. TYP MAX. MIN. TYP. MAX.
A 0.90 1.45 35.4 57.1
A1 0.00 0.10 0.0 3.9
A2 0.90 1.30 35.4 51.2
b 0.35 0.50 13.7 19.7
C 0.09 0.20 3.5 7.8
D 2.80 3.00 110.2 118.1
E 1.50 1.75 59.0 68.8
e0.95 37.4
H 2.60 3.00 102.3 118.1
L 0.10 0.60 3.9 23.6
SOT23-5L MECHANICAL DATA
7049676C
.
LD2981 SERIES
14/17
DIM. mm. mils
MIN. TYP MAX. MIN. TYP. MAX.
A 1.4 1.6 55.1 63.0
B 0.44 0.56 17.3 22.0
B1 0.36 0.48 14.2 18.9
C 0.35 0.44 13.8 17.3
C1 0.35 0.44 13.8 17.3
D 4.4 4.6 173.2 181.1
D1 1.62 1.83 63.8 72.0
E 2.29 2.6 90.2 102.4
e 1.42 1.57 55.9 61.8
e1 2.92 3.07 115.0 120.9
H 3.94 4.25 155.1 167.3
L 0.89 1.2 35.0 47.2
SOT-89 MECHANICAL DATA
P025H
LD2981 SERIES
15/17
DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 180 7.086
C 12.8 13.0 13.2 0.504 0.512 0.519
D 20.2 0.795
N 60 2.362
T 14.4 0.567
Ao 3.13 3.23 3.33 0.123 0.127 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 3.9 4.0 4.1 0.153 0.157 0.161
P 3.9 4.0 4.1 0.153 0.157 0.161
Tape & Reel SOT23-xL MECHANICAL DATA
LD2981 SERIES
16/17
DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 180 7.086
C 12.8 13.0 13.2 0.504 0.512 0.519
D 20.2 0.795
N 60 2.362
T 14.4 0.567
Ao 4.70 4.80 4.90 0.185 0.189 0.193
Bo 4.30 4.40 4.50 0.169 0.173 0.177
Ko 1.70 1.80 1.90 0.067 0.071 0.075
Po 3.9 4.0 4.1 0.153 0.157 0.161
P 7.9 8.0 8.1 0.311 0.315 0.319
Tape & Reel SOT89 MECHANICA L DATA
LD2981 SERIES
17/17
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the
conseq uences of u se of such inform ation nor fo r an y infr ingeme nt of pa tents or oth er righ ts of third part ies whic h may resul t from
its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications
mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information
previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or
systems without express written approval of STMicroelectronics.
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