Datasheet

© 2008 Microchip Technology Inc. DS21949C-page 19
TC1303A/TC1303B/TC1303C/TC1304
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 TC1303 LDO Shutdown Input Pin
(SHDN2
)
SHDN2 is a logic-level input used to turn the LDO
Regulator on and off. A logic-high (> 45% of V
IN
), will
enable the regulator output. A logic-low (< 15% of V
IN
)
will ensure that the output is turned off.
3.2 TC1304 Shutdown Input Pin
(SHDN
)
SHDN is a logic-level input used to initiate the
sequencing of the LDO output, then the buck regulator
output. A logic-high (> 45% of V
IN
), will enable the
regulator outputs. A logic-low (< 15% of V
IN
) will ensure
that the outputs are turned off.
3.3 LDO Input Voltage Pin (V
IN2
)
V
IN2
is a LDO power input supply pin. Connect variable
input voltage source to V
IN2
. Connect V
IN1
and V
IN2
together with board traces as short as possible. V
IN2
provides the input voltage for the LDO. An additional
capacitor can be added to lower the LDO regulator
input ripple voltage.
3.4 LDO Output Voltage Pin (V
OUT2
)
V
OUT2
is a regulated LDO output voltage pin. Connect
a 1 µF or larger capacitor to V
OUT2
and A
GND
for proper
operation.
3.5 Power-Good Output Pin (PG)
PG is an output level indicating that V
OUT2
(LDO) is
within 94% of regulation. The PG output is configured
as a push-pull for the TC1303B and open-drain output
for the TC1303A, TC1303C and TC1304.
3.6 Analog Ground Pin (A
GND
)
A
GND
is the analog ground connection. Tie A
GND
to the
analog portion of the ground plane (A
GND
). See the
physical layout information in Section 5.0 “Application
Circuits/Issues” for grounding recommendations.
3.7 Buck Regulator Output Sense Pin
(V
FB
/V
OUT1
)
For V
OUT1
adjustable-output voltage options, connect
the center of the output voltage divider to the V
FB
pin.
For fixed-output voltage options, connect the output of
the buck regulator to this pin (V
OUT1
).
Pin No.
Symbol
DescriptionTC1303 TC1304
MSOP, DFN MSOP, DFN
1 SHDN2
— Active Low Shutdown Input for LDO Output Pin
1 — SHDN Active Low Shutdown Input both Buck Regulator Output and LDO Output.
Initiates sequencing up and down
2V
IN2
V
IN2
Analog Input Supply Voltage Pin
3V
OUT2
V
OUT2
LDO Output Voltage Pin
4 PG PG Power-Good Output Pin
5A
GND
A
GND
Analog Ground Pin
6V
FB
/V
OUT1
V
FB
/V
OUT1
Buck Feedback Voltage (Adjustable Version) / Buck Output Voltage
(Fixed Version) Pin
7 SHDN1 — Active Low Shutdown Input for Buck Regulator Output Pin
7—A
GND
Analog Ground Pin
8V
IN1
V
IN1
Buck Regulator Input Voltage Pin
9L
X
L
X
Buck Inductor Output Pin
10 P
GND
P
GND
Power Ground Pin
11 EP EP Exposed Pad - For the DFN package, the center exposed pad is a thermal
path to remove heat from the device. Electrically this pad is at ground
potential and should be connected to A
GND
.