LP8345CDT-3.3/NOPB National Semiconductor, LP8345CDT-3.3/NOPB Datasheet - Page 10

• Manufacturer Part Number: LP8345CDT-3.3/NOPB
• Description: IC REG LDO CMOS 500MA 3.3V 3DPAK
• Manufacturer: National Semiconductor

Specifications of LP8345CDT-3.3/NOPB

• Regulator Topology: Positive Fixed
• Voltage - Output: 3.3V
• Voltage - Input: Up to 10V
• Voltage - Dropout (typical): 0.27V @ 500mA
• Number Of Regulators: 1
• Current - Output: 500mA
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: TO-252-2, DPak (2 Leads + Tab), TO-252AA, SC-63
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Other names: *LP8345CDT-3.3; *LP8345CDT-3.3/NOPB; LP8345CDT-3.3

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Applications Section
GENERAL INFORMATION
The LP8345 is a low-dropout, low quiescent current linear
regulator. As shown in Figure 1 it consists of a 1.25V refer-
ence, error amplifier, MOSFET driver, PMOS pass transistor
and for the fixed output versions, an internal feedback net-
work (R
load by a thermal shutdown circuit and a foldback current
limit circuit.
The 1.25V reference is connected to the inverting input of
the error amplifier. Regulation of the output voltage is
EXTERNAL CAPACITOR
An Input capacitor of 1µF or greater is required between the
LP8345 V
bypassing of the V
(i.e. 10µF) can provide improved bypassing of power supply
noise.
Stable operation can be achieved with an output capacitor of
1µF or greater, either ceramic X7R dielectric or aluminum/
tantalum electrolytic. While the minimum capacitor value is
1µF, the typical output capacitor values selected range from
1µF to 10µF. The larger values provide improved load-
transient response, power supply rejection and stability.
OUTPUT VOLTAGE SETTING (ADJ VERSION ONLY)
The output voltage is set according to the amount of nega-
tive feedback (Note that the pass transistor inverts the feed-
back signal). This feedback is determined by R
the resulting output voltage represented by the following
equation:
1
/R
IN
2
). In addition, the device is protected from over-
pin and ground. While 1µF will provide adequate
IN
supply larger values of input capacitor
FIGURE 1. LP8345 Functional Block Diagram
1
and R
2
with
10
achieved by means of negative feedback to the non-
inverting input of the error amplifier. Feedback resistors R
and R
ing on whether it is a fixed voltage version or the adjustable
version. The negative feedback and high open loop gain of
the error amplifier cause the two inputs of the error amp to be
virtually equal in voltage. If the output voltage changes due
to load changes, the error amplifier and MOSFET driver
provide the appropriate drive to the pass transistor to main-
tain the error amplifier’s inputs as virtually equal.
Use the following equation to determine the values of R
R
MINIMUM LOAD CURRENT
A minimum load of 100µA is required for regulation and
stability over the entire operating temperature range. If ac-
tual load current fall below 100µA it is recommended that a
resistor of value R
ground.
2
for a desired V
2
are either internal or external to the device, depend-
OUT
L
=V
(R
O
/100µA be placed between V
2
= 100kΩ is recommended).
20064803
O
1
and
and
1