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LT3689IMSE-PBF

Description
700mA Step-Down Regulator with Power-On Reset and Watchdog Timer
File Size380KB,32 Pages
ManufacturerLinear ( ADI )
Websitehttp://www.analog.com/cn/index.html
Download Datasheet View All

LT3689IMSE-PBF Overview

700mA Step-Down Regulator with Power-On Reset and Watchdog Timer

FEATURES
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LT3689/LT3689-5
700mA Step-Down
Regulator with Power-On Reset
and Watchdog Timer
DESCRIPTION
The LT
®
3689 is an adjustable frequency (350kHz to 2.2MHz)
monolithic step-down switching regulator with a power-on
reset and watchdog timer. The regulator operates from
inputs up to 36V and withstands transients up to 60V. Low
ripple Burst Mode
®
operation maintains high efficiency at
low output current while keeping output ripple below 15mV
in a typical application, with input quiescent current of just
85μA. Shutdown circuitry reduces input supply current to
less than 1μA while EN/UVLO is pulled low. Using a resis-
tor divider on the EN/UVLO pin provides a programmable
undervoltage lockout. Current limit, frequency foldback
and thermal shutdown provide fault protection.
The reset and watchdog timeout periods are indepen-
dently adjustable using external capacitors. Tight accuracy
specifications and glitch immunity ensure reliable reset
operation of a system without false triggering. The open
collector
RST
will pull down if output voltage drops 10%
below the programmed value. The watchdog timer is
pin-selectable for window or timeout modes. In timeout
mode,
WDO
pulls low if too long of a period passes before
a watchdog transition is detected. In window mode, the
LT3689 monitors for WDI falling edges grouped too close
together or too far apart.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Wide Input Range:
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits through
60V Transients
85μA I
Q
at 12V
IN
to 3.3V
OUT
Low Ripple Burst Mode
®
Operation Allows Output
Ripple <15mV
P-P
Programmable, Defeatable Watchdog Timer with
Window or Timeout Control
Programmable Power-On Reset Timer (POR)
Synchronizable, Adjustable 350kHz to 2.2MHz
Switching Frequency
700mA Output Switching Regulator with Internal
Power Switch
Fixed 5V or Adjustable Output Voltage
800mV Feedback Voltage
Programmable Input Undervoltage Lockout with
Hysteresis
16-Pin 3mm
×
3mm QFN and 16-Pin MSOP Packages
APPLICATIONS
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Automotive Electronic Control Units
Industrial Power Supplies
TYPICAL APPLICATION
3.3V Regulator with Power-On Reset Timer and Watchdog Timer
V
IN
4.5V TO 36V
TRANSIENT TO 60V
μP
I/O
I/O
RESET
C
WDT
10nF
t
WDU
= 182ms
t
WDL
= 5.9ms
WDI
WDO
RST
C
WDT
C
POR
68nF
t
RST
= 157ms
C
POR
GND
LT3689
DA
FB
RT
SYNC
f
SW
= 700kHz
3689 TA01
Efficiency
90
V
IN
= 12V
80 V
OUT
= 3.3V
f = 700kHz
70 L = 12μH
T
A
= 25°C
60
50
40
30
20
10
0
0.0001
0.001
0.01
0.1
LOAD CURRENT (A)
1
3689 TA01b
1000
2.2μF
V
IN
EN/UVLO
OUT
BST
SW
POWER LOSS (mW)
10pF
316k
3.3V
700mA
EFFICIENCY (%)
0.1μF
12μH
100
10
20.5k
100k
22μF
1
3689fa
1

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