LTC3626
8
3626fa
For more information www.linear.com/LTC3626
pin FuncTions
BOOST (Pin 1): Boosted Floating Driver Supply Pin. The
(+) terminal of the external bootstrap capacitor connects
to this pin while the (–) terminal connects to the SW pin.
The normal operation voltage swing of this pin ranges
from INTV
CC
to PV
IN
+ INTV
CC
.
INTV
CC
(Pin 2): Internal 3.3V Regulator Output Pin. This
pin should be decoupled to PGND with a low ESR ceramic
capacitor of value 1µF or greater. The 3.3V regulator is
disabled when the RUN pin is low.
V
ON
(Pin 3): On-Time Voltage Input. This pin sets the
voltage trip point for the on-time comparator. Tying this
pin to the output voltage makes the on-time proportional
to V
OUT
when V
OUT
< 6V. When V
OUT
> 6V, the switching
frequency may become higher than the set frequency. The
impedance of this pin is nominally 160kΩ.
TSET (Pin 4): Temperature Limit Set Pin. The voltage at
this pin determines the threshold for internal temperature
shutdown. When the voltage at TMON reaches the volt
-
age at TSET, the LTC3626 will trigger an overtemperature
fault. An overtemperature fault will initiate part shutdown,
reset soft-start and an attempt to restart once the internal
temperature falls 10°C (typical) from the threshold given at
TSET. The voltage at TSET has no impact on a secondary
overtemperature shutdown threshold within the LTC3626
as described in Note 4 of the Electrical Characteristics
section.
TMON (Pin 5): Temperature Monitor Output. A voltage
proportional to the measured on-die temperature will ap
-
pear at this pin. The voltage-to-temperature scaling factor
is 200°K/V.
See the Applications Information section for
detailed information on the TMON function. Tie this pin to
INTV
CC
to disable the temperature monitor circuit.
SGND (Pin 6): Signal Ground Pin. This pin should have a
low noise connection to reference ground. The feedback
resistor network, external compensation network, current
monitor components, and R
T
resistor should be connected
to this ground.
IMON
IN
(Pin 7): Average Input Current Monitor. A current
proportional to the average input current flows out of this
pin. Pull this pin to INTV
CC
to defeat the input current moni-
tor function. An error amplifier compares the voltage on
this pin to 1.2V
(typical) and throttles the average current
as required based on the external resistor value from this
pin to SGND. Selecting the external resistor value allows
the user to control the maximum average input current.
See the Applications Information section for more details.
IMON
OUT
(Pin 8): Average Output Current Monitor Pin. A
current proportional to the average output current flows
out of this pin. Pull this pin to INTV
CC
to defeat the output
current monitor function. An error amplifier compares
the voltage on this pin to 1.2V (typical) and throttles the
average current as required based on the external resis
-
tor value from this pin to SGND. Selecting the external
resistor value allows the user to control the maximum
average output current.
See the Applications Information
section for more details.
TRACK/SS (Pin 9): Output Voltage Tracking and Soft-Start
Input. Forcing a voltage below 0.6V on this pin overrides the
internal reference input to the error amplifier. The LTC3626
will servo the FB pin to the TRACK/SS voltage under this
condition. Above 0.6V, the tracking function stops and the
internal reference resumes control of the error amplifier. An
internal 1.4µA (typical) pull-up current from INTV
CC
allows
a soft-start function to be implemented by connecting an
external capacitor between this pin and ground. See the
Applications Information section for more details.
FB (Pin 10): Output Voltage Feedback. This pin is the input
to the error amplifier that compares the feedback voltage
to the internal 0.6V reference voltage. Connect this pin to
the appropriate resistor divider network to program the
desired output voltage.
