LTC3388-3 Linear Technology, LTC3388-3 Datasheet - Page 13

• Manufacturer Part Number: LTC3388-3
• Description: 20V High Efficiency Nanopower Step-Down Regulator
• Manufacturer: Linear Technology

DataSheet.in
OPERATION
Enable and Standby Modes
Two logic pins, EN and STBY, determine the operating
mode of the LTC3388-1/LTC3388-3. When EN is high and
STBY is low the synchronous buck converter is enabled
and will regulate the output if the input voltage is above
the programmed output voltage and above the UVLO
threshold. If EN is low the buck converter circuitry is
powered down to save quiescent current. The internal rail
generation circuits are kept alive and the voltages at V
and CAP are maintained. When low, EN also shuts down
the PGOOD circuitry and pulls the PGOOD pin low. If EN
is high and the input falls below the UVLO threshold, the
buck converter is shut down.
While enabled, the LTC3388-1/LTC3388-3 can be placed
in standby mode by bringing STBY high. In standby mode
the buck converter is disabled, eliminating the quiescent
current used to run the buck circuitry. The PGOOD and
sleep comparators are kept alive to maintain the state of
the PGOOD pin.
AC-COUPLED
50mV/DIV
STANDBY
5V/DIV
V
OUT
0V
V
L = 22μH, C
STANDBY TRANSIENT
Figure 4. LTC3388-3 Standby Transient,
V
IN
OUT
= 5.5V,
= 3.3V, I
OUT
= 100μF
LOAD
IN2
500μs/DIV
= 5mA
The sleep comparator has lower quiescent current than the
PGOOD comparator and when the LTC3388-1/LTC3388-3
is in sleep mode the PGOOD comparator is shut down and
PGOOD is held high. The same occurs in standby mode.
If the LTC3388-1/LTC3388-3 was in sleep before entering
standby it will stay in sleep in standby, saving the quiescent
current of the PGOOD comparator. If V
sleep falling threshold the PGOOD comparator will be
enabled. If V
the PGOOD pin will be pulled low.
If STBY is driven high with EN low it will be ignored and
the LTC3388-1/LTC3388-3 will remain shut down.
If EN and STBY are driven high but near V
V
additional quiescent current is typically 40nA and depends
on V
will prevent additional quiescent current on V
Figure 4 shows V
standby. While in standby, the buck is off and V
quiet.
IL
, additional quiescent current may appear on V
IN
and temperature. Driving EN or STBY to 0V or V
338813 F04
LTC3388-1/LTC3388-3
OUT
falls below the PGOOD falling threshold
OUT
during a transition into and out of
OUT
IH
or low but near
falls below the
IN
.
13
IN
OUT
. This
338813f
IN2
is