LT3582 LINER [Linear Technology], LT3582 Datasheet - Page 16

• Manufacturer Part Number: LT3582
• Description: I2C Programmable Boost and Single Inductor Inverting DC/DC Converters with OTP
• Manufacturer: LINER [Linear Technology]

LT3582/LT3582-5/LT3582-12
APPLICATIONS INFORMATION
under control of its respective RAMP pin (see Figure 8
below). The power-up sequencing concludes when both
outputs have reached regulation.
Evaluating PUSEQ Settings (LT3582 Only): After SHDN
rises, the LT3582 uses the PUSEQ confi guration found
in OTP. The effects of differing PUSEQ settings can be
observed without writing to OTP by taking the following
actions:
This will initiate the desired power-up sequence that can
be observed with an oscilloscope.
Power-Down Discharge (PDDIS bit)
The PDDIS bit is used to enable power down discharge.
This bit is pre-confi gured to a “1” for the LT3582-5 and
LT3582-12, thus enabling power-down discharge.Setting
16
1. Write the SWOFF bit high, stopping both converters
2. Write the desired settings to the PUSEQ bits in
3. Set the RSEL2 bit high which selects the REG2
4. Write SWOFF low which restarts both converters.
and discharging the RAMP pins.
REG2.
confi guration settings.
0.5V/DIV
0.5V/DIV
V
V
V
V
5V/DIV
5V/DIV
RAMPN
RAMPP
VOUTN
VOUTP
Figure 8: Power-up Sequencing (PUSEQ=10)
RAMPP
5ms/DIV
RAMPN
PDDIS = 0 disables the power-down discharge causing
the chip to shut down immediately after SHDN falls. The
PDDIS bit must only be set in conjunction with PUSEQ being
set to 11. Driving SHDN low, with power-down discharge
enabled (PDDIS = 1) causes the chip to power-down after
fi rst discharging the output voltages. Specifi cally, driving
SHDN low causes the following sequence of events to
happen:
1. Both converters are turned off.
2. Discharge currents are enabled to discharge the
3. The chip waits until the output voltages have
4. Discharge currents are disabled and the LT3582
output capacitors
• See Electrical Charateristics for I
• See Electrical Charateristics for I
discharged to within ~0.5V to ~1.5V of ground.
powers down.
I
helps discharge V
3582512 F08
CAPP-PDS
which help discharge V
OUTN
VOUTN-PDS
OUTP
VOUTP-PDS
and CAPP
which
3582512f
and