LTC2927_15 Datasheet, PDF (1/16 Pages) Linear Technology – Single Power Supply Tracking Controller

FEATURES
n _{Flexible Power Supply Tracking}
n _{Tracks Both Up and Down}
n _{Power Supply Sequencing}
n _{Supply Stability is Not Affected}
n _{Low Pin Count}
n _{Controls Single Supply without Series FETs}
n _{Adjustable Ramp Rate}
n _{Supply Shutdown Output}
n _{Available in 8-Lead ThinSOT™ and 8-Lead}
(3mm × 2mm) DFN Packages
U
APPLICATIO S
n _{VCORE and VI/O Supply Tracking}
n _{Microprocessor, DSP and FPGA Supplies}
n _{Multiple Supply Systems}
n _{Point-of-Load Supplies}
LTC2927
Single Power Supply
Tracking Controller
DESCRIPTIO
The LTC^®2927 provides a simple solution to power supply
tracking and sequencing requirements. By selecting a few
resistors, the supply can be configured to ramp-up and
ramp-down with differing ramp rates, voltage offsets, or
time delays relative to other supplies or a master signal.
By forcing current into a feedback node of an independent
supply, the LTC2927 causes the output to track a ramp
signal without inserting any pass element losses. Because
the current is controlled in an open-loop manner, the
LTC2927 does not affect the transient response or stabil-
ity of the supply. The compact solution at point of load
minimizes the trace length of the DC/DC circuit sensitive
FB node. Furthermore, it presents a high impedance when
power-up is complete, effectively removing it from the
DC/DC circuit.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Patents Pending.
TYPICAL APPLICATIO
EARLY V_IN
3.3V
138k
100k
16.5k
13k
V_CC
ON
RAMP
LTC2927
0.1μF
0.1μF VIN
SDO
RAMPBUF
FB
RUN/SS IN
DC/DC
FB = 1.235V
OUT
1.8V
TRACK
GND
35.7k
16.5k
EARLY V_IN
3.3V
887k
412k
V_CC
ON
RAMP
LTC2927
SDO
RAMPBUF
FB
0.1μF
V_IN
RUN/SS IN
DC/DC
FB = 0.8V
OUT
2.5V
TRACK
GND
2927 TA01a
412k
887k
Track-Up and Track-Down Waveforms
1V/DIV
RAMP
(3.3V)
2.5V
1.8V
RAMP
(3.3V)
2.5V
1.8V
10ms/DIV
2927 TA01b
1V/DIV
10ms/DIV
2927 TA01c
2927fb
1