LP3921 Datasheet, PDF (25/41 Pages) National Semiconductor (TI) – Battery Charger Management and Regulator Unit with Integrated Boomer® Audio Amplifier

LP3921
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PROGRAMMING INFORMATION
SNVS580A – AUGUST 2008 – REVISED MAY 2013
Enable via Serial Interface
Table 17. Register Address 8h'00: OP_EN
BIT
NAME
FUNCTION
0
LDO1_EN
Bit set to '0' - LDO disabled
2
LDO3_EN
Bit set to '1' - LDO enabled
3
LDO7_EN
Note that the default setting for this Register is [0000 0101]. This shows that LDO1 and LDO3 are enabled by
default whereas LDO7 is not enabled by default on start up.
Table 18. LDO Output Programming⁽¹⁾
Register Add (hex)
01
02
03
04
05
06
07
Name
LDO1PGM
O/P
LDO2PGM
O/P
LDO3PGM
O/P
LDO4PGM
O/P
LDO5PGM
O/P
LDO6PGM
O/P
LDO7PGM
O/P
Data Range (hex)
03 - 0F
00 - 0F
05 - 0C
00 - 0F
05 - 0C
05 - 0C
00 - 0F
Output Voltage
1.5V to 3.3V
(def. 1.8V)
2.5V to 3.3V
(def 3.0V)
2.7V to 3.05V
(def 3.0V)
1.5V to 3.3V
(def 3.0V)
2.7V to 3.05V
(def 3.0V)
2.7V to 3.05V
(def 3.0V)
1.5V to 3.3V
(def 3.0V)
(1) See Table 4 for full programmable range of values.
EXTERNAL CAPACITORS
The Low Drop Out Linear Voltage regulators on the LP3921 require external capacitors to ensure stable outputs.
The LDO's on the LP3921 are specifically designed to use small surface mount ceramic capacitors which require
minimum board space. These capacitors must be correctly selected for good performance
INPUT CAPACITOR
Input capacitors are required for correct operation. It is recommended that a 10 µF capacitor be connected
between each of the voltage input pins and ground (this capacitance value may be increased without limit). This
capacitor must be located a distance of not more than 1 cm from the input pin and returned to a clean analogue
ground. A ceramic capacitor is recommended although a good quality tantalum or film capacitor may be used at
the input.
WARNING
Important: Tantalum capacitors can suffer catastrophic failures due to surge
current when connected to a low-impedance source of power (like a battery or a
very large capacitor). If a tantalum capacitor is used at the input, it must be
guaranteed by the manufacturer to have surge current rating sufficient for the
application. There are no requirements for the ESR (Equivalent Series
Resistance) on the input capacitor, but tolerance and temperature coefficient
must be considered when selecting the capacitor to ensure the capacitance will
remain within its operational range over the entire operating temperature range
and conditions.
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