LT3582 LINER [Linear Technology], LT3582 Datasheet - Page 15

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

APPLICATIONS INFORMATION
disconnect current limit being reached D) additional ring-
ing occurs when the CAPP pin starts charging E) output
voltage overshoot occurs because the inductor currents
are maximized during the output ramp up.
In some cases it may be desirable to use only one RAMP
pin capacitor. In cases where PUSEQ = 11 (see Power-Up
Sequencing section) the RAMPP & RAMPN pins can be
connected together and to a single capacitor. In this case
the capacitor will charge with twice the current confi gured
by the IRMP bits.
Ramping V
the unique ability to generate a smooth V
ramp starting from ground and continuing all the way up
to regulation (see Figure 6). This ability is not possible
with typical Boost converters in which the output is taken
from the cathode of the Schottky diode (CAPP node in
Figure 5).
The LT3582 series incorporates an output disconnect
PMOS allowing V
V
IN
0.2V/DIV
0.2A/DIV
Figure 6: V
V
2V/DIV
2V/DIV
RAMPP
V
CAPP
C1
OUTP
I
L2
L1
OUTP
SWP
Figure 5: Boost Converter Topology
OUTP
OUTP
from Ground: The LT3582 series has
D1
C2
Soft-Start Ramping from Ground
to be grounded during shutdown.
CAPP
5μs/DIV
DISCONNECT
CONTROL
LT3582
SERIES
3582512 F06
OUTP
C3
LOAD
voltage
3582512 F05
V
OUTP
Once enabled, the Disconnect Control circuit actively
drives the PMOS gate allowing V
as shown in Figure 6. Once V
the PMOS is fully turned “on” to reduce resistance and
improve effi ciency.
Power-Up Sequencing (PUSEQ bits)
Once enabled, the part requires a delay of T
typ) to properly confi gure itself. Once confi gured, the order
in which V
by the PUSEQ bits. The combinations available for the
LT3582 are shown in Table 2. The LT3582-5/LT3582-12
are pre-confi gured with the 11 combination.
Table 2. Power-Up Sequences
Selecting the 01 or 10 combinations cause one of the out-
puts to start ramping shortly after SHDN rises. The ramp
rate of V
the Soft-Start section. After V
tion voltage, the remaining output is activated and ramps
PUSEQ[1:0] Power-Up Sequence
LT3582/LT3582-5/LT3582-12
00
01
10
11
Figure 7: V
0.2A/DIV
0.5V/DIV
V
OUT
3V/DIV
3V/DIV
RAMPP
V
CAPP
OUTP
OUTP
I
L2
is controlled by the RAMP pin as discussed in
Outputs are disabled, neither output ramps up
V
V
Both V
same time.
OUTN
OUTP
OUTP
B
and V
ramps up 1st, followed by V
ramps up 1st, followed by V
OUTP
Soft-Start with Excessive Ramp Rate
C
OUTN
D
& V
A
50μs/DIV
ramp to regulation is controlled
OUTN
OUT
ramp up starting at the
OUTP
E
OUTP
nears its target regula-
reaches regulation,
to ramp up linearly
3582512 F07
OUTP
OUTN
STARTUP
15
(64μs
3582512f