LTC3620 Datasheet, PDF (7/16 Pages) Linear Technology – Ultralow Power 15mA Synchronous Step-Down Switching Regulator

LTC3620
PIN FUNCTIONS
SW (Pin 1): Switch Node Connection to Inductor. This pin
connects to the internal power MOSFET Switches.
GND (Pin 2): Ground Connection for Internal Circuitry and
Power Path Return. Tie directly to local ground plane.
FMIN/MODE (Pin 3): Frequency Clamp Select Input. Driv-
ing this pin with a 20kHz to 300kHz external clock sets the
minimum switching frequency. Pulling this pin low sets
the minimum switching frequency to the internally set
50kHz. Pulling this pin high defeats the minimum switching
frequency and allows the part to switch at arbitrarily low
frequencies dependent on the load current.
LOBATB (Pin 4): Low-Battery Status Output. This open-
drain output pulls low when V_IN falls below 3V.
NC (Pin 5): No Connect.
V_FB (Pin 6): Regulator Feedback Pin. This pin receives
the feedback voltage from the resistive divider across the
output. For the LTC3620-1, this pin must be connected
directly to V_OUT. V_OUT is internally divided from V_OUT to the
reference voltage of 0.6V as seen in the Block Diagram.
RUN (Pin 7): Regulator Enable Pin. Apply a voltage greater
than 0.8V to enable the regulator. Do not float this pin.
V_IN (Pin 8): Input Supply Pin. Must be locally bypassed.
Exposed Pad (Pin 9): GND. Must be soldered to PCB.
BLOCK DIAGRAM
V_IN
8
RUN
7
FMIN/MODE
3
LOBAT
3V
UVLO
SELECT
50kHz
LOBATB
4
V_IN
PEAK INDUCTOR
8
CURRENT ADJUST
SHUTDOWN
ICMP
PFD
SW
SWITCH
DRIVER
1
0.6V
V_FB
(LTC3620)
6
V_FB
(LTC3620-1)
6
EAMP
RCMP
2 _{3620 BD}
GND
3620f
7