參數(shù)資料
型號(hào): LTC1778-1
廠商: Linear Technology Corporation
英文描述: Wide Operating Range, No RSENSE Step-Down Controller
中文描述: 寬工作,無(wú)檢測(cè)電阻范圍步降控制器
文件頁(yè)數(shù): 1/24頁(yè)
文件大?。?/td> 303K
代理商: LTC1778-1
1
LTC1778/LTC1778-1
Wide Operating Range,
No R
SENSE
1778fa
TM
Step-Down Controller
I
No Sense Resistor Required
I
True Current Mode Control
I
Optimized for High Step-Down Ratios
I
t
ON(MIN)
100ns
I
Extremely Fast Transient Response
I
Stable with Ceramic C
OUT
I
Dual N-Channel MOSFET Synchronous Drive
I
Power Good Output Voltage Monitor (LTC1778)
I
Adjustable On-Time (LTC1778-1)
I
Wide V
IN
Range: 4V to 36V
I
±
1% 0.8V Voltage Reference
I
Adjustable Current Limit
I
Adjustable Switching Frequency
I
Programmable Soft-Start
I
Output Overvoltage Protection
I
Optional Short-Circuit Shutdown Timer
I
Micropower Shutdown: I
Q
< 30
μ
A
I
Available in a 16-Pin Narrow SSOP Package
APPLICATIU
I
Notebook and Palmtop Computers
I
Distributed Power Systems
The LTC
1778 is a synchronous step-down switching
regulator controller optimized for CPU power. The con-
troller uses a valley current control architecture to deliver
very low duty cycles with excellent transient response
without requiring a sense resistor. Operating frequency is
selected by an external resistor and is compensated for
variations in V
IN
.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference, and can assist second-
ary winding regulation by disabling discontinuous opera-
tion when the main output is lightly loaded.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is user program-
mable. Wide supply range allows operation from 4V to 36V
at the input and from 0.8V up to (0.9)V
IN
at the output.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No R
SENSE
is a trademark of Linear Technology Corporation.
Figure 1. High Efficiency Step-Down Converter
Efficiency vs Load Current
+
D
CMDSH-3
D1
B340A
L1
1.8
μ
H
C
VCC
4.7
μ
F
C
IN
10
μ
F
50V
×
3
V
5V TO 28V
V
2.5V
10A
+
C
OUT
180
μ
F
4V
×
2
M2
Si4874
1778 F01a
M1
Si4884
R
ON
1.4M
C
SS
0.1
μ
F
I
ON
V
IN
TG
SW
BOOST
RUN/SS
I
TH
SGND
INTV
CC
BG
PGND
V
FB
PGOOD
C
B
0.22
μ
F
R
C
20k
LTC1778
C
500pF
R2
30.1k
R1
14k
LOAD CURRENT (A)
0.01
E
80
90
1778 F01b
70
60
0.1
1
10
100
V
IN
= 5V
V
OUT
= 2.5V
V
IN
= 25V
DESCRIPTIOU
FEATURES
TYPICAL APPLICATIO
U
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