LD2981 series
Ultra low drop voltage regulators with inhibit
Low ESR output capacitors compatible
Feature summary
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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; 3.0; 3.3; 3.6;
3.8; 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
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.
SOT23-5L
SOT-89
Description
The LD2981 series are 100mA fixed-output
voltage regulator. The low drop-voltage and the
Schematic diagram
July 2006
Rev. 12
1/22
www.st.com
22
LD2981 series
Contents
1
2
3
4
5
6
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1
6.2
6.3
6.4
6.5
6.6
External capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Inhibit input operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Reverse current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7
8
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Order code
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22
LD2981 series
Pin configuration
1
Figure 1.
Pin configuration
Pin connections (top view)
SOT23-5L
TO-92
Table 1.
Pin N°
SOT23-5L
1
2
3
4
5
Pin description
Pin N°
SOT-89
3
2
Symbol
V
IN
GND
INHIBIT
NC
1
V
OUT
Input port
Ground pin
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
Not connected
Output port
Name and Function
Table 2.
Symbol
R
thJC
R
thJA
Thermal data
Parameter
Thermal resistance junction-case
Thermal resistance junction-ambient
SOT23-5L
81
255
SOT-89
15
110
Unit
°C/W
°C/W
3/22
PCB Design
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