LTC3458L Linear Technology, LTC3458L Datasheet - Page 7

• Manufacturer Part Number: LTC3458L
• Description: 1.7A/ 1.5MHz Synchronous Step-Up DC/DC Converter with Output Disconnect
• Manufacturer: Linear Technology

PI FU CTIO S
SW (Pin 1): Switch Pin for Inductor Connection. During
discontinuous conduction mode an antiring resistor con-
nects SW to V
V
supply and decouple with 1µF minimum.
SYNC (Pin 3): Oscillator Synchronization Pin. A clock
pulse width of 100ns to 2µs is required to synchronize the
internal oscillator. This pin is disabled when grounded.
SHDN (Pin 4): Shutdown Pin. Grounding this pin shuts
down the IC. Connect to >1.25V to enable.
I
resistor from I
current according to the following formula:
where I
R
oscillator frequency, according to the formula:
where f
Oscillator frequency can be programmed between 400kHz
and 1.5MHz.
FB (Pin 7): Connect Resistor Divider Tap Here. The output
voltage can be adjusted from 2V to 6V. Feedback reference
voltage is typically 1.225V.
COMP (Pin 8): g
pensation network is connected from this pin to ground to
LIM
IN
T
I
U
f
(Pin 6): Connect a resistor to ground to program the
LIMIT
OSC
(Pin 2): Input Supply Pin. Connect this to the input
(Pin 5): Adjustable Peak Current Limit. Connect a
LIMIT
OSC
=
=
U
0 2 0 004
is in MHz and R
R
.
180
is in amps and R
ILIM
IN
+
LIM
to reduce noise.
m
.
1
to GND to program the peak inductor
Error Amp Output. A frequency com-
U
•
R
T
T
is in kΩ.
T
is in kΩ.
compensate the loop. See the section “Compensating the
Feedback Loop” for guidelines.
GND (Pin 9): Signal Ground Pin.
SS (Pin 10): Connect a capacitor between this pin and
ground to set soft-start period. 5µA of current is sourced
from SS during soft-start.
BURST (Pin 11): Burst Mode Threshold Adjust Pin. A
resistor/capacitor combination from this pin to ground
programs the average load current at which automatic
Burst Mode operation is entered, according to the formula:
where R
where C
To force fixed frequency PWM mode, connect BURST to
V
V
Internal Gate Drive Source for the Power Switches.
Exposed Pad (PGND) (Pin 13): Must be soldered to PCB
ground, for electrical contact and optimum thermal
performance.
OUT
OUT
t(msec) = C
R
C
V
OUT
BURST
BURST
through a 51k resistor.
(Pin 12): Output of the Synchronous Rectifier and
BURST(MIN)
BURST
=
1 225 1
=
=
.
I
C
BURST
SS
is in kΩ and I
OUT
10
10 000
⎛
⎜
⎝
(µF )• 200
,
and C
+
•
R
V
R
OUT
1
2
⎞
⎟
⎠
OUT
BURST
are in µF.
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is in amps.
LTC3458L
7
3458lf