ltc3523-ltc3523-2 Linear Technology Corporation, ltc3523-ltc3523-2 Datasheet - Page 6

• Manufacturer Part Number: ltc3523-ltc3523-2
• Description: Synchronous 600ma Step-up And 400ma Step-down Dc/dc Converters
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LTC3523/LTC3523-2
SW1 (Pin 5): Step-Up Converter Switch Pin. Connect the
inductor between SW1 and V
lengths as short and wide as possible to reduce EMI and
voltage overshoot. If the inductor current falls to zero or
⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 is low, an internal 100Ω anti-ringing switch is
connected from SW1 to V
GND1 (Pin 6): Step-Up Converter Power Ground. Connect
this pin to the ground plane.
GND2 (Pin 7): Step-Down Converter Power Ground. Con-
nect this pin to the ground plane.
SW2 (Pin 8): Step-Down Converter Switch Pin. Connect
one end of the inductor to SW2. Keep these PCB trace
lengths as short and wide as possible to reduce EMI and
voltage overshoot.
V
This pin can be connected to a different supply than V
This pin must be connected to a valid supply voltage.
MODE (Pin 10): Step-Up and Step-Down Converter Mode
Selection Pin. Do not leave this pin fl oating.
• MODE = Low: PWM mode
• MODE = High: Automatic Burst Mode operation
PGOOD2 (Pin 11): Step-Down Converter Power Good
Comparator Output. This open-drain output is pulled low
when V
FB2 (Pin 12): Step-Down Converter Feedback Input to the
Error amplifi er. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 0.6V to 5.5V by:
See Block Diagram.
6
IN2
V
(Pin 9): Step-Down Converter Power Voltage Input.
OUT(STEP-DOWN)
FB2
< –9% of its regulation voltage.
=
0 6
.
IN1
V
•
to minimize EMI.
IN1
⎛
⎝ ⎜
1
+
. Keep these PCB trace
R
R
3
4
⎞
⎠ ⎟
IN1
.
If large feedback resistors, above 500k are used, then it
will be necessary to use a lead capacitor connected to the
output voltage and FB2.
⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 (Pin 13): Step-Down Converter Logic Controlled
Shutdown Input. Do not leave this pin fl oating.
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 = High: Normal free-running operation,
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 = Low: Shutdown, quiescent current < 1μA.
This pin cannot exceed the voltage on V
GND3 (Pin 14): Analog Ground. The feedback voltage
dividers for each converter must be returned to GND3
for best performance.
Note: When laying out your PCB provide a short direct
path between GND1 and the (–) side of the step-up output
capacitor(s) and GND2 and the step-down output capaci-
tor.These pins are not connected together internally.
V
the higher of V
⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 (Pin 16): Step-Up Converter Logic Controlled
Shutdown Input.
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 = High: Normal free-running operation,
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 = Low: Shutdown, quiescent current < 1μA.
This pin cannot exceed the voltage on V
Exposed Pad (Pin 17): Die attach pad must be soldered
to PCB ground for electrical contact and optimum thermal
performance.
BAT
1.2MHz/2.4MHz typical operating frequency.
1.2MHz/2.4MHz typical operating frequency.
(Pin 15): Analog Voltage Input. Connect this pin to
IN1
or V
IN2
.
IN2
IN1
.
.
3523f