LTC2923
Power Supply
Tracking Controller
Fea T Descrip T
n
Flexible Power Supply Tracking
The LTC 2923 provides a simple solution to power supply
n
Tracks Both Up and Down
tracking and sequencing requirements. By selecting a few
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Power Supply Sequencing
resistors, the supplies can be configured to ramp-up and
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Supply Stability is Not Affected
ramp-down together or with voltage offsets, time delays
n
Controls Two Supplies Without Series FETs
or different ramp rates.
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Controls a Third Supply With a Series FET
By introducing currents into the feedback nodes of two
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Adjustable Ramp Rates
independent switching regulators, the LTC2923 causes
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Electronic Circuit Breaker
their outputs to track without inserting any pass element
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Available in 10-Lead MS and 12-Lead
losses. Because the currents are controlled in an open-
(4mm 3mm) DFN Packages
loop manner, the LTC2923 does not affect the transient
response or stability of the supplies. Furthermore, it
a T
presents a high impedance when power-up is complete,
n
V and V Supply Tracking effectively removing it from the DC/DC circuit.
CORE I/O
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Microprocessor, DSP and FPGA Supplies
For systems that require a third supply, one supply can
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Servers
be controlled with a series FET. This optional series FET
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Communication Systems
can also control a supply that does not allow direct ac-
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
cess to its feedback resistors (e.g., a power module) or
Technology Corporation. All other trademarks are the property of their respective owners.
Patents Pending.
a supply whose output cannot be forced to ground (e.g.,
a 3-terminal linear regulator). When the FET is used, an
electronic circuit breaker provides protection from short-
circuit conditions.
Typical a T
Q1
V
IN
3.3V
3.3V
3.3V
2.5V
1V/DIV
1.8V
10nF
V
IN
IN
138k V RAMP
GATE
CC
DC/DC
2923 TA02
1ms/DIV
ON FB1 FB = 1.235V OUT 1.8V
100k
LTC2923
16.5k
35.7k
RAMPBUF STATUS
V
16.5k IN
3.3V
TRACK1 SDO
2.5V
IN
1V/DIV
887k
1.8V
13k
DC/DC
TRACK2 FB2 FB = 0.8V OUT 2.5V
GND
412k
887k
412k
2923 TA02b
1ms/DIV
2923 TA01
2923fb
1
For more information www.linear.com/LTC2923
ion pplica
ions pplica
ion uresLTC2923
a Te Maxi Mu M r a T (Note 1)
Supply Voltage (V ) ................................ 0.3V to 10V Average Current
CC
Input Voltages TRACK1, TRACK2 ................................................5mA
ON ......................................................... 0.3V to 10V FB1, FB2 ...............................................................5mA
TRACK1, TRACK2 ........................0.3V to V + 0.3V RAMPBUF ............................................................5mA
CC
RAMP .............................................0.3V to V + 1V Operating Temperature Range
CC
Output Voltages LTC2923C ................................................ 0C to 70C
FB1, FB2, SDO, STATUS ......................... 0.3V to 10V LTC2923I .............................................40C to 85C
RAMPBUF ....................................0.3V to V + 0.3V Storage Temperature Range .................. 65C to 150C
CC
GATE (Note 2) ......................................0.3V to 11.5V Lead Temperature (Soldering, 10 sec)
MS Package ......................................................300C
K / D F Ma T
TOP VIEW
V 1 12 RAMP
CC
ON 2 11 GATE
TOP VIEW
V 1 10 RAMP
TRACK1 3 10 STATUS
CC
ON 2 9 GATE 13
TRACK2 4 9 SDO
TRACK1 3 8 FB1
TRACK2 4 7 FB2
RAMPBUF 5 8 FB1
RAMPBUF 5 6 GND
GND 6 7 FB2
MS PACKAGE
10-LEAD PLASTIC MSOP
DE12 PACKAGE
T = 125C, = 120C/W
JMAX JA
12-LEAD (4mm 3mm) PLASTIC DFN
T = 125C, = 43C/W
JMAX JA
EXPOSED PAD (PIN 13)
(PCB GND CONNECTION OPTIONAL)
o r Der i n F Ma T