ltc3100 Linear Technology Corporation, ltc3100 Datasheet - Page 9

• Manufacturer Part Number: ltc3100
• Description: 1.5mhz Synchronous Dual Channel Dc/dc Converter And 100ma Ldo
• Manufacturer: Linear Technology Corporation

TYPICAL PERFORMANCE CHARACTERISTICS
PIN FUNCTIONS
SWBST (Pin 1): Switch Pin for the Boost Converter.
Connect the boost inductor between SWBST and V
Keep PCB trace lengths as short and wide as possible to
reduce EMI. If the inductor current falls to zero, an internal
anti-ringing switch is connected from SWBST to V
to minimize EMI.
V
(which is the drain of the internal synchronous rectifi er)
and Input Voltage for the LDO. PCB trace length from V
to the output fi lter capacitor (4.7μF minimum) should be
as short and wide as possible.
V
a 1μF ceramic capacitor between V
values of capacitance may be used for higher PSRR or
improved transient response.
SWBK (Pin 4): Switch Pin for the Buck Converter. Connect
the buck inductor between SWBK and the buck output
fi lter capacitor. Keep PCB trace lengths as short and wide
as possible to reduce EMI.
V
nect a minimum of 4.7μF ceramic decoupling capacitor
from this pin to ground.
PGBK (Pin 6): Open-Drain Output That Pulls Low When
FBBK Is More Than 8% Below Its Regulated Voltage. Con-
BST
LDO
INBK
(Pin 3): Output Voltage of the LDO Regulator. Connect
(Pin 2): Output Voltage for the Boost Converter
(Pin 5): Input Voltage for the Buck Converter. Con-
0.625
0.600
0.550
0.525
0.500
0.575
1
RUN Pin Threshold Voltage
1.5
2
2.5
FALLING
RISING
V
IN
LDO
3
(V)
3.5
and GND. Larger
4
4.5
3100 G27
5
INBST
INBST
BST
.
nect a pull-up resistor from this pin to a positive supply
less than 6V.
GND (Pin 7): Signal Ground. Provide a short, direct PCB
path between GND and the PC board ground plane con-
nected to the Exposed Pad.
RUNBK (Pin 8): Logic-Controlled Shutdown Input for the
Buck Converter. There is an internal 4MΩ pull-down on
this pin.
RUNBK = High: Normal operation
RUNBK = Low: Shutdown
FBBK (Pin 9): Feedback Input to the g
for the Buck Converter. Connect the resistor divider tap
to this pin. The output voltage can be adjusted from 0.6V
to 5.5V by:
RUNLDO (Pin 10): Logic-Controlled Shutdown Input for
the LDO Regulator. There is an internal 4MΩ pull-down
on this pin.
RUNLDO = High: Normal operation
RUNLDO = Low: Shutdown
450
400
300
350
250
200
150
100
V
50
0
OUT BUCK
0.5
Start-Up Delay Times vs V
_
1
T
1.5
A
= 25°C, unless otherwise specifi ed.
2
=
0 600
2.5
V
.
IN
BUCK
(V)
3
V
3.5
•
BOOST
LDO
⎛
⎝ ⎜
IN
4
1
+
4.5
3100 G28
R
R
6
5
5
⎞
⎠ ⎟
m
LTC3100
Error Amplifi er
9
3100f