LP3925 Datasheet, PDF (28/51 Pages) Texas Instruments – High Performance Power Management Unit for Handset Applications

LDO Information
There are altogether 15 LDOs in LP3925 grouped as:
• General-type “PERFECT” LDOs;
• WILO-type LDOs;
• MICRO-PWR LDO; and
• USB LDO.
All LDOs can be programmed through serial interface for dif-
ferent output voltage values which are summarized in the
“Control Register Bit Description” tables.
At the PMU power on, LDOs start up according to the selected
startup sequence and the default voltages. See section Pow-
er-on and Power-On Sequences for details.
For stability all LDOs need to have external capacitors COUT
connected to the output with recommended value of 1µF . It
is important to select the type of capacitor which capacitance
will in no case (voltage, temperature, etc) be outside of limits
specified in the LDO Electrical Characteristics.
The description of different LDO types follow, except for the
RTC description in the following section.
GENERAL-TYPE “PERFECT” LDOs
The general “PERFECT” LDOs are optimized to supply both
analog and digital loads having ULTRA LOW NOISE (10
µV_RMS for I_OUT > 5mA) and excellent PSRR (75 dB at 10 kHz)
performance. They can be programmed through the serial in-
terface for different output voltage values.
For fast discharging of the output capacitors in shutdown, an
internal 300Ω pull-down resistor to ground can be set via pro-
gram control.
In sleep mode quiescent current is lowered to 5µA for energy
saving; in this mode these LDOs should not be loaded by
more than 3-5mA of output current.
The innovative design of these general type LDOs reduces
the sensitivity to the placement of the output capacitor. These
general purpose LDOs do not need the output capacitor to be
placed as close to the PMU as is the case for normal LDOs.
If a (1µF or more) capacitor is attached to a circuit load there
is no need to place an output capacitor at the PMU.
WILO-TYPE LDOs
Wide Input Low Output (WILO) LDOsThe WILO-type LDO is
optimized for wide range supply and low output voltage. It has
good dynamic performance to supply different fast changing
(digital) loads.
For proper operation, an input voltage of more than 2V is
necessary. Hence, voltage drop on pass transistor (dropout
voltage) will always exceed 0.45V and is independent of out-
put current (in specified current range).
For fast discharge of the output capacitors in shut down, an
internal 300Ω pull-down resistor to ground can be set via pro-
gram control
MICRO-PWR LDO
This LDO is primarily used for internal supply purposes and
fixed to 1.8V, but may deliver up to 30 mA of current also
externally. This LDO is ON even in Standby mode (with total
PMU current consumption about 2µA) and user may use it to
supply some backup/always on system(s).
USB LDO
USB LDO is a high voltage LDO that uses VIN_CHG as a
supply. It is used as a supply for D+ and D- buses as well as
the VTRM output. It has a 28V over voltage protection capa-
bility. Regulator provides 45 dB PSRR at 10 kHz on entire
voltage selection range except 4.85V option. Here it is 30 dB
and is due to small distance to supply.
GENERAL LDO ELECTRICAL CHARACTERISTICS
Typical values and limits appearing in normal type apply for T_J = 25°C. Limits appearing in boldface type apply over the entire
junction temperature range for operation, T_J = −40°C to +125°C. Unless otherwise specified, the following applies for V_BATT = 3.6V.
(Note 6)
Symbol
Parameter
Conditions
LDO# Typ.
Limits
Min Max
Units
V_OUT
Output Voltage Accuracy
I_OUT = 1mA, V_OUT = 2.0V
1...10
-2
2
%
-3
3
4,8
80
I_MAX
Output Current Rating
1..3,
5..7, 9,
10
mA
300
V_OUT +0.5V ≤ V_IN ≤ 4.5V
4,8
300
80
mA
(Note 7)
I_SC
Output Current Limit
V_OUT +0.5V ≤ V_IN ≤ 4.5V
1..3,
5..7, 9,
650
300
mA
(Note 7)
10
I_SLEEP
I_Q
V_DO
Output Current in sleep mode V_OUT +0.5V ≤ V_IN ≤ 4.5V 1..10
Quiescent current in sleep mode
5
Dropout Voltage
V_OUT = 3V;
I_OUT = I_MAX (Note 8)
4, 8
60
1..3,
4..7, 9, 100
10
3
mA
µA
150
mV
200
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