參數(shù)資料
型號: LTC1574CS
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode
中文描述: 1 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PDSO16
封裝: 0.150 INCH, PLASTIC, SO-16
文件頁數(shù): 4/8頁
文件大?。?/td> 226K
代理商: LTC1574CS
4
LTC1574
LTC1574-3.3/LTC1574-5
PI
FU
CTIO
N
S
U
U
NC (Pins 1, 8, 9, 16):
No Connection.
GND (Pins 2, 4, 13, 15):
Ground.
SW (Pins 3, 14):
Drain of P-Channel MOSFET Switch and
Cathode of Schottky Diode.
V
IN
(Pin 5):
Input Supply Voltage. It must be decoupled
close to ground (Pin 4).
I
PGM
(Pin 6):
This pin selects the current limit of the
P-channel switch. With I
PGM
= V
IN
, the current trip point is
600mA and with I
PGM
= 0V, the current trip point is
reduced to 340mA.
SHDN (Pin 7):
Pulling this pin to ground keeps the internal
switch off and puts the LTC1574 in micropower shutdown.
V
OUT
or V
FB
(Pin 10):
For the LTC1574, this pin connects
t
o the main voltage comparator input. On the LTC1574-5
and LTC1574-3.3, this pin goes to an internal resistive
divider which sets the output voltage
.
LB
OUT
(Pin 11):
Open drain of an N-Channel Pull-Down.
This pin will sink current when (Pin 12) LB
IN
goes below
1.25V.
LB
IN
(Pin 12):
The (–) Input of the Low-Battery Voltage
Comparator. The (+) input is connected to a reference
voltage of 1.25V.
APPLICATIO
S I
FOR
ATIO
U
Operating Frequency and Inductor
Since the LTC1574 utilizes a constant off-time architecture,
its operating frequency is dependent on the value of V
IN
. The
frequency of operation can be expressed as:
W
U
U
f
t
V
V
V
V
Hz
OFF
IN
OUT
IN
D
=
+
( )
1
where t
OFF
= 4
μ
s and V
D
is the voltage drop across the
internal Schottky diode. Note that the operating frequency
is a function of the input and output voltage.
Although the size of the inductor does not affect the fre-
quency or inductor peak current, it does affect the ripple
current. The peak-to-peak ripple current is given by:
I
V
V
L
RIPPLE
OUT
D
=
+
)
4 10
6
A
P-P
By choosing a smaller inductor, a low ESR (Effective Series
Resistance) output filter capacitor has to be used. Core loss
will increase due to higher ripple current.
Short-Circuit Protection
The LTC1574 is protected from output short circuits by its
internal current limit. Depending on the condition of the
Low-Battery Detector
The low-battery indicator senses the input voltage through
an external resistive divider. This divided voltage connects
to the “–” input of a voltage comparator (Pin 12) which is
compared with a 1.25V reference voltage. With the current
I
PGM
pin, the limit is either set to 340mA or 600mA. In
addition, the off-time of the switch is increased to allow the
inductor current to decay far enough to prevent any current
build-up (see Figure 1).
I
PGM
= V
IN
I
PGM
= 0
GND
L = 100
μ
H
V
IN
= 13.5V
1
20
μ
s/DIV
1574 F01
Figure 1. Inductor Current with Output Shorted
相關PDF資料
PDF描述
LTC1574CS-5 High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode
LTC1574 High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode(可調輸出,高效率步降DC/DC變換器(內部帶肖特基二極管))
LTC1574-3.3 High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode(3.3V,高效率步降DC/DC變換器(內部帶肖特基二極管))
LTC1589IG 12-/14-/16-Bit SoftSpan DACs with Programmable Output Range
LTC1592 12-/14-/16-Bit SoftSpan DACs with Programmable Output Range
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