LTC4425EDD LINER [Linear Technology], LTC4425EDD Datasheet - Page 11

• Manufacturer Part Number: LTC4425EDD
• Description: Linear SuperCap Charger with Current-Limited Ideal Diode and V/I Monitor
• Manufacturer: LINER [Linear Technology]

OPERATION
Output Status Monitor
The LTC4425 has an internal comparator to always monitor
the output voltage V
7.5% of its fi nal programmed value in LDO mode or more
than 250mV below the input voltage V
rent profi le mode, the comparator reports the power-fail
condition by pulling the same open-drain output PFO low.
When both input and output voltages are good for at least
200ms, the PFO pin goes high impedance and can be
pulled up to any external supply by a resistor to indicate
a power good situation. In normal mode, the load should
not exceed 1/10th of the programmed charge current
until PFO is high.
V
If for some reason V
not present and the EN pin is pulled high, most of the
circuitry including the voltage clamp circuitry is kept alive
and the part draws about 20μA from the output capaci-
tors. However, the internal leakage balancer is turned off
under this condition.
OUT
> V
IN
Operation
OUT
IN
. At any time, if V
falls below V
OUT
IN
OUT
or the input is
in charge cur-
falls below
Shutdown Mode
The LTC4425 can be shut down by pulling the EN pin low.
In shutdown mode, very minimal circuitry is alive and
the part draws less than 2μA from the supply or from the
output capacitors if the supply is not present.
Charge Current Soft-Start
The LTC4425 includes a soft-start circuit to minimize
the inrush current at the start of a charge cycle. When a
charge cycle is initiated, the charge current ramps from
zero to full-scale over a period of approximately 1ms and
this soft-start can be monitored by observing the PROG
pin voltage. This has the effect of minimizing the transient
current load on the power supply during start-up.
Thermal Shutdown
The LTC4425 includes a thermal shutdown circuit in ad-
dition to the thermal regulator. If for any reason, the die
temperature exceeds 160°C, the entire part shuts down.
It resumes normal operation once the temperature drops
by about 14°C, to approximately 146°C.
LTC4425
11
4425p