Datasheet
PAD
2
6
3
4
5
1
7
8
9
11
16
15
14
13
12
10
17
18
19
20
21
22
23
24
25
26
27
28
PVIN
SW
SW
SW
SW
PVIN
PGND
PGND
PGND
COMP
FREQ
EN
AGND
FB
PGOOD
PGND
AGND
AGND
AGND
AGND
2V5
AVIN
AVIN
AGND
5V0
CBOOT
PVIN
PVIN
LM21305
SNVS639F –DECEMBER 2009–REVISED MARCH 2013
www.ti.com
DESCRIPTION (CONTINUED)
The LM21305 offers flexible system configuration with programmable switching frequency from 300 kHz to 1.5
MHz using one resistor or via external clock synchronization. On-chip bias supply sub-regulators alleviate the
need for external bias power and simplify PCB layout. The device also offers internal soft-start to limit inrush
current, pre-biased and monotonic startup capability, cycle-by-cycle current limiting, and thermal shutdown. Peak
current-mode control with a high-gain error amplifier maintains stability throughout the entire input voltage and
load current ranges and enables excellent line and load transient response.
Offered in a thermally enhanced WQFN-28 package, the LM21305 features internal output over-voltage and
over-current protection circuits for increased system reliability. A precision enable pin and integrated input UVLO
allow the turn-on of the device to be tightly controlled and sequenced. An integrated open-drain power good
indicator provides power rail sequencing capability and fault indication.
Connection Diagram
Figure 1. WQFN-28 Package, Exposed Pad
Package Number RSG
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Product Folder Links: LM21305