LTC3426 Datasheet, PDF (4/12 Pages) Linear Technology – 1.2MHz Step-Up DC/DC Converter in SOT-23

LTC3426
PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor between SW and
V_IN. A Schottky diode is connected between SW and V_OUT.
Keep these PCB trace lengths as short and wide as
possible to reduce EMI and voltage overshoot. If the
inductor current falls to zero, an internal 100Ω antiringing
switch is connected from SW to V_IN to minimize EMI.
GND (Pin 2): Signal and Power Ground. Provide a short
direct PCB path between GND and the (–) side of the output
capacitor(s).
FB (Pin 3): Feedback Input to the g_m Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
SHDN (Pin 4): Logic Controlled Shutdown Input.
SHDN = High: Normal free running operation
SHDN = Low: Shutdown, quiescent current < 1µA
Typically, SHDN should be connected to V_IN through a 1M
pull-up resistor.
V_OUT (Pin 5): Output Voltage Sense Input. The NMOS
switch gate drive is derived from the greater of V_OUT and
V_IN.
V_IN (Pin 6): Input Supply. Must be locally bypassed.
V_OUT = 1.22 • ^{⎛⎝⎜}1+ _RR21^{⎞⎠⎟}
BLOCK DIAGRA
1.22V
REFERENCE
+
A1
–
3
FB
V_OUT
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
V_OUT
V_IN
COMPARATOR
5
6
–
R_C
A2
C_C
+
PWM LOGIC
AND DRIVER
Σ
RAMP
GENERATOR
SHDN
4
SHUTDOWN AND
SOFT-START
1.2MHz
OSCILLATOR
Figure 1
SW
1
0.02Ω
2
3426 F01
GND
3426f
4