LT3697_15 Datasheet, PDF (1/32 Pages) Linear Technology – USB 5V, 2.5A Output, 35V Input Buck with Cable Drop Compensation

LT3697
Features
USB 5V, 2.5A Output,
35V Input Buck with
Cable Drop Compensation
Description
n _{Accurate 5V Output}
n _{Programmable Cable Drop Compensation}
n _{Programmable Output Current Limit}
n _{Adjustable Output from 5.0V to 6.1V}
n _{Dual Input Feedback Permits Regulation on Output}
of USB Switch
n _{Active Load Reduces Output Overshoot}
n _{FLT Flag Indicates Overcurrent on the USB Output}
n _{1.5ms FLT Flag Delay Filters Hot Plug Events}
n _{USB Output Current Monitor}
n _{Wide Input Rage: Operation from 5V to 35V}
n _{Withstands Input Transient to 60V}
n _{2.5A Maximum Output Current}
n _{Survives Output Short to GND and Car Battery}
n _{Adjustable Switching Frequency: 300kHz to 2.2MHz}
n _{Synchronizable from 300kHz to 2.2MHz}
n _{Small, Thermally Enhanced 16-Lead MSOP Package}
Applications
n _{Automotive USB}
n _{Industrial USB}
The LT^®3697 is a 35V, 2.5A step-down switching regulator
designed to power 5V USB applications. A precise output
voltage and programmable cable drop compensation
maintain accurate 5V regulation at the USB socket connected
to the end of a long cable. The accurate, programmable
current limit can eliminate the need for a USB power switch
and improve system reliability. The provided 180mA active
load reduces output overshoot during load transients. Dual
feedback allows regulation on the output of a USB switch
and limits cable drop compensation to a maximum of 6.1V
output, protecting USB devices during fault conditions. A
separate 5V output can be taken from the SYS terminal
to power auxiliary circuitry such as a USB hub controller.
The LT3697 also provides a load current monitor output
and an overcurrent fault indicator.
The LT3697 operates from 300kHz to 2.2MHz and with-
stands input voltage transients up to 60V. The device's
output survives shorts to ground and to the battery. A current
mode topology is used for fast transient response and good
loop stability. Shutdown reduces input supply current to
less than 1µA. The LT3697 is available in a 16-lead MSOP
package with an exposed pad for low thermal resistance.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Typical Application
5V Step-Down Converter with Cable Drop Compensation and Output Current Limit
V_IN 6V TO 35V
TRANSIENT TO 60V
255k
330pF
10µF
7.5k
1nF
V_IN BST
EN
SW
LT3697
FLT
SYS
RT
ISP
VC
ISN
RLIM
USB5V
SYNC
RCBL
GND
1µF
10µH
16.5k
V_OUT
0.022Ω
4 METERS AWG 20
TWISTED PAIR CABLE
0.13Ω
47µF
10nF 10k
+
V_LOAD
5V, 2.5A
+
100µF
–
0.13Ω
3697 TA01
For more information www.linear.com/LT3697
Transient Response
5.75
6.0
V_OUT
5.50
5.0
5.25
4.0
V_LOAD
5.00
3.0
I_LOAD
4.75
25mA/µs ^2.0
4.50
250µs/DIV
1.0
3697 TA01a
3697f
1