LTC1701B_15 Datasheet, PDF (4/12 Pages) Linear Technology – 1MHz Step-Down DC/DC Converters in SOT-23

LTC1701/LTC1701B
PI FU CTIO S
SW (Pin 1): The Switch Node Connection to the Inductor.
This pin swings from V_IN to a Schottky diode (external)
voltage drop below ground. The cathode of the Schottky
diode must be closely connected to this pin.
GND (Pin 2): Ground Pin. Connect to the (–) terminal of
C_OUT, the Schottky diode and (–) terminal of C_IN.
V_FB (Pin 3): Receives the feedback voltage from the
external resistive divider across the output. Nominal volt-
age for this pin is 1.25V.
I_TH/RUN (Pin 4): Combination of Error Amplifier Compen-
sation Point and Run Control Input. The current compara-
tor threshold increases with this control voltage. Nominal
voltage range for this pin is 1.25V to 2.25V. Forcing this
pin below 0.8V causes the device to be shut down. In
shutdown all functions are disabled.
V_IN (Pin 5): Main Supply Pin and the (+) Input to the
Current Comparator. Must be closely decoupled to ground.
Pin Limit Table
PIN
NAME
1
SW
2
GND
3
V_FB
4
I_TH/RUN
5
V_IN
DESCRIPTION
Switch Node
Ground Pin
Output Feedback Pin
Error Amplifier Compensation and RUN Pin
Main Power Supply
NOMINAL (V)
MIN TYP MAX
– 0.3
V_IN
0
0
1.25 1.35
0
2.25
2.5
5.5
ABSOLUTE MAX (V)
MIN
MAX
V_IN – 8.5
V_IN + 0.3
– 0.3
3
– 0.3
3
– 0.3
6
BLOCK DIAGRA
V_REF
I_TH/RUN
V_REF
V_FB
+
I_TH/REF
CLAMP
–
+
ERROR
AMP
–
V_IN
50µA
V_IN
1.25V
BANDGAP
REFERENCE
V_REF
(1.25V)
1.5V
SHDN
(1.25V TO 2.25V)
+
I_TH
COMP
–
(LTC1701 only)
+
OVER
VOLTAGE
1.4V
– ^COMP
PULSE
STRETCHER
V_FB < 0.6V
V_IN
+
CURRENT
COMP
–
V_REF
+
CURRENT
SENSE
AMP _–
OFF-TIMER
AND GATE
CONTROL LOGIC
GATE
DRIVER
GND
SW
1701 BD
4