LTC3458L Datasheet, PDF (8/16 Pages) Linear Technology – 1.7A, 1.5MHz Synchronous Step-Up DC/DC Converter with Output Disconnect

LTC3458L
BLOCK DIAGRA
SYNC 3
R_T 6
BURST
SW
V_IN
11
1
2
V_IN
OSC/SYNC
MAX
DUTY
SLOPE
I_ZERO
PWM
AND
BURST MODE
DRIVE LOGIC
P-DRIVE
N-DRIVE
UNDER
MODE
SLEEP
MODE
FIXED
FREQUENCY
BURST MODE
MUX
SLEEP
CONTROL
I_{COMP/LIMIT_PEAK}
I_{BURST_PEAK}
SLOPE
BURST MODE
CONTROL
I_ZERO
DETECT
ANTIRING
N-DRIVE
P-DRIVE ^VSELECT
–
+
V_BEST ^SW1
SLEEP TO
ALL BLOCKS
PEAK CURRENT
COMPARATOR
I_COMP, I_LIMIT,
I_{BURST_PEAK},
SLOPE COMP
I_SENSE
P-DRIVE
UNDER
4%
UNDERVOLTAGE
PGND
ERROR AMPLIFIER/
BURST COMPARATOR
BURST ACTIVE
–
(DISABLED IN
BURST MODE)
+
MODE
BIAS
CURRENTS
UVLO
TSD
V_IN
REFERENCE/
BIAS
12 VOUT
7 FB
V_BEST
SOFT-START
THERMAL SD
SD
N-DRIVE
PGND
9
5
13
10
8
4
GND
I_LIM
PGND
SS
COMP SHDN
SDB
TO ALL BLOCKS
3458L BD
APPLICATIO S I FOR ATIO
Detailed Description
The LTC3458L provides high efficiency, low noise power
for boost applications with output voltages up to 6V. The
true output disconnect feature eliminates inrush current,
and allows V_OUT to go to zero during shutdown. The
current mode architecture with adaptive slope compensa-
tion provides ease of loop compensation with excellent
transient load response. The low R_DS(ON), low gate charge
synchronous switches eliminate the need for an external
Schottky rectifier, and provide efficient high frequency
pulse width modulation (PWM) control. High efficiency is
achieved at light loads when Burst Mode operation is
entered, where the IC’s quiescent current is a low 12µA
typical on V_IN. The LTC3458L is designed to provide
custom performance in a variety of applications with
programmable feedback, current limit, oscillator frequency,
soft-start, and Burst Mode threshold.
LTC3458L Programmable Functions
Current Limit (I_LIMIT)/Peak Burst Current (I_BURSTPEAK).
The programmable current limit circuit sets the maximum
peak current in the internal N-channel MOSFET switch.
This clamp level is programmed using a resistor to ground
on I_LIM. In Burst Mode operation, the current limit is
automatically set to ~1/4 of the programmed current limit
for optimal efficiency. An 84.5k R_ILIM resistor is recom-
mended in most applications unless a lower limit is
needed to prevent the external inductor from saturating.
I_LIMIT
=
180
R
I is in amps and R is in kΩ.
I_BURSTPEAK
≈
1
4
• I_LIM
3458lf
8