LTC3527 Linear Technology Corporation, LTC3527 Datasheet - Page 8

• Manufacturer Part Number: LTC3527
• Description: 1.2MHz/2.2MHz Synchronous Step-Up DC/DC Converters
• Manufacturer: Linear Technology Corporation

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LTC3527/LTC3527-1
PIN FUNCTIONS
⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 (Pin 1): Boost Converter 1 Logic-Controlled
Shutdown Input. There is an internal 4MΩ pull-down on
this pin.
Note: Both converters must be shut down together to
achieve < 2µA quiescent current.
FB1 (Pin 2): Boost Converter 1 Feedback Input to the g
Error Amplifi er. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 1.6V to 5.25V by:
MODE (Pin 3): Logic-Controlled Mode Input for Both
Boost Converters.
MODE pin must be 1V or greater to ensure fi xed frequency
over all operating conditions.
V
Input and Drain of the Internal Synchronous Rectifi er
MOSFET. Driver bias is derived from V
length from V
be as short and wide as possible.
SW1 (Pin 6): Boost Converter 1 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
SW2 (Pin 7): Boost Converter 2 Switch Pin. Connect the
inductor between SW2 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 ⎯ 2 is low, an internal 100Ω anti-ringing switch is
connected from SW2 to V
V
Input and Drain of the Internal Synchronous Rectifi er
8
OUT1
OUT2
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 = High: Normal free running operation,
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 = Low: Shutdown, quiescent current < 2µA.
• MODE = High: Fixed frequency operation
• MODE = Low: Automatic Burst Mode operation
V
1.2MHz/2.2MHz typical operating frequency.
OUT1
(Pin 5): Boost Converter 1 Output Voltage Sense
(Pin 8): Boost Converter 2 Output Voltage Sense
=
1 20
.
OUT1
V
to the output fi lter capacitor(s) should
•
⎡
⎢
⎣
1
+
R
R
IN1
IN2
2
1
⎤
⎥
⎦
to minimize EMI.
to minimize EMI.
IN1
IN2
(
. Keep these PCB trace
. Keep these PCB trace
See Block Diagram
OUT1
. PCB trace
)
m
MOSFET. Driver bias is derived from V
length from V
be as short and wide as possible.
FSEL (Pin 10): Logic-Controlled Frequency Select
Input.
FB2 (Pin 11): Boost Converter 2 Feedback Input to the
g
pin. The output voltage can be adjusted from 1.6V to
5.25V by:
⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 (Pin 12): Boost Converter 2 Logic-Controlled
Shutdown Input. There is an internal 4MΩ pull-down on
this pin.
Note: Both converters must be shut down together to
achieve < 2µA quiescent current.
PGOOD2 (PIN 13): Boost Converter 2 Power Good Com-
parator Output. This open-drain output is low when V
is 9% below its regulation voltage.
GND (Pin 14): Signal Ground. This pin is used as a
ground reference for the internal circuitry of the LTC3527/
LTC3527-1.
V
Operation section for more information.
PGOOD1 (PIN 16) Boost Converter 1 Power Good Com-
parator Output. This open-drain output is low when V
is 9% below its regulation voltage.
Exposed Pad (Pin 17): Backplane. The Exposed Pad is
PGND and must be soldered to the PCB ground plane.
It serves as the power ground connection for V
V
package.
m
IN
OUT2
• FSEL = High: 2.2MHz Operation
• FSEL = Low: 1.2MHz Operation
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 = High: Normal free-running operation,
• ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 = Low: Shutdown, quiescent current < 2µA.
V
, V
Error Amplifi er. Connect resistor divider tap to this
1.2MHz/2.2MHz typical operating frequency.
OUT2
IN1
, and as a means of conducting heat away from the
, V
=
IN2
1 20
OUT2
.
(Pins 15, 4, 9): Battery Input Voltage. See
V
to the output fi lter capacitor(s) should
•
⎡
⎢
⎣
1
+
R
R
3
4
⎤
⎥
⎦
(
See Block Diagram
OUT2
. PCB trace
OUT1
35271f
and
)
FB
FB