LTC2925IUF#PBF Linear Technology, LTC2925IUF#PBF Datasheet - Page 11

• Manufacturer Part Number: LTC2925IUF#PBF
• Description: IC POWER SUPPLY CONTROLLER 24QFN
• Manufacturer: Linear Technology

Specifications of LTC2925IUF#PBF

• Applications: Power Supply Controller
• Voltage - Supply: 2.9 V ~ 5.5 V
• Current - Supply: 1.5mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Voltage Supervisor Type: Power Supply Tracker
• Number Of Voltage Supervisors: 4
• Operating Supply Voltage (min): 2.9V
• Operating Supply Voltage (max): 5.5V
• Operating Temperature Classification: Industrial
• Operating Temp Range: -40C to 85C
• Pin Count: 24
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Input: -
• Lead Free Status / Rohs Status: Compliant

APPLICATIONS INFORMATION
pin is pulled low, the supplies are latched off, and the
FAULT pin is held low until the fault is cleared by taking
the ON pin below 0.4V.
The PGI pin, which is normally connected to the RST pin of
an external supply monitor, is pulled up with 10μA through
a Schottky diode allowing it to be pulled safely above V
Since, PGTMR pulls up with a 10μA current source, the
capacitor, C
timeout duration, t
If the power good timeout circuit is unused, tie PGTMR
low and fl oat PGI.
The Ramp Buffer
The RAMPBUF pin provides a buffered version of the
RAMP pin voltage that drives the resistive dividers on the
TRACKx pins. When there is no external FET, it provides
up to 3mA to drive the resistors even though the GATE
pin only supplies 10μA (Figure 8). The RAMPBUF pin
also proves useful in systems with an external FET. Since
the track cell drives 0.8V on the TRACKx pins, if R
connected directly to the FET’s source, the TRACKx pin
could potentially pull up the FET’s source towards 0.8V
when the FET is off. RAMPBUF blocks this path.
Shutdown Outputs
In some applications it might be necessary to control
the shutdown or RUN/SS pins of the slave supplies. The
LTC2925 may not be able to supply the rated 1mA of current
from the FB1, FB2, and FB3 pins when V
If the slave power supplies are capable of operating at low
input voltages, use the open-drain SDx outputs to drive
the SHDN or RUN/SS pins of the slave supplies (Figures 7
C
PGTMR
PGTMR
=
10
μA t
, required to confi gure the power good
1 23
PGTMR
.
•
PGTMR
V
, is determined from:
CC
is below 2.9V.
TBx
CC
is
.
and 8). The SDx pins are released when the ON pin rises
above 1.23V, V
condition, and there are no faults latched. The shutdown
timer begins at the same time, and the supplies begin to
ramp up after the shutdown timer cycle completes. The
duration of the timer cycle is confi gured by a capacitor
tied between SDTMR and GND. The capacitor voltage is
ramped up by a 10μA current source and the SDTMR
cycle completes when its voltage reaches 1.23V. Thus, the
capacitor, C
cycle, t
The SDx pins pull low again when the ON pin is pulled
below 1.23V and the RAMP pin is below about 100mV.
R
R
V
R
TB1
TA1
C
IN
TA2
SDTMR
V
V
IN
IN
Figure 8. Typical Application Without External FET
R
R
R
SDTMR
R
R
TB2
ONB
ONA
TB3
TA3
0.1μF
SDTMR
=
ON
REMOTE
STATUS
FAULT
V
RAMPBUF
TRACK1
TRACK2
TRACK3
GND
, is determined from:
CC
10
CC
SENSEP SENSEN
SCTMR
μA t
is above the 2.6V undervoltage lockout
, required for a given shutdown timer
1 23
.
•
SDTMR
LTC2925
SDTMR
V
C
SDTMR
GATE
PGTMR
C
GATE
C
PGTMR
RAMP
SD1
SD3
SD2
FB1
FB2
FB3
PGI
LTC2925
R
R
R
2925 F08
RST
RUN/SS
FB
RUN/SS
FB
RUN/SS
FB
FA1
FA2
FA3
MONITOR
SUPPLY
DC/DC
DC/DC
DC/DC
R
R
R
FB1
FB3
FB2
V
V
V
IN
OUT
IN
OUT
IN
OUT
IN
IN
IN
11
2925fc
SLAVE1
SLAVE2
SLAVE3