TC1268 MICROCHIP [Microchip Technology], TC1268 Datasheet - Page 4

• Manufacturer Part Number: TC1268
• Description: 500mA Fixed Output, Fast Response CMOS LDO with Shutdown
• Manufacturer: MICROCHIP [Microchip Technology]

TC1268
DS21379B-page 4
2.0
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
3.0
The TC1268 is a precision, fixed output LDO. Unlike
bipolar regulators, the TC1268 supply current does
not increase with load current. In addition, V
remains stable and within regulation over the entire
0mA to I
consideration in RTC and CMOS RAM battery back-up
applications). Figure 3-1 shows a typical application
circuit.
FIGURE 3-1:
3.1
The turn on response is defined as two separate
response categories, Wake-up Time (T
Time (T
The TC1268 has a fast Wake-up Time (5µsec typical)
when released from shutdown. See Figure 3-2 for the
Wake-up Time designated as T
is defined as the time it takes for the output to rise to 2%
of the V
Battery
(8-Pin SOIC)
Pin No.
S
OUT
1
2
3
4
5
6
7
8
C1 required only if ERROR is used
as a processor RESET signal (See Text)
).
PIN DESCRIPTIONS
DETAILED DESCRIPTION
Turn On Response
LOAD
+
–
C
10nF
BYP
value after being released from shutdown.
MAX
+
PIN FUNCTION TABLE
C
1µF
load current range, (an important
IN
BYPASS
Symbol
ERROR
SHDN
V
GND
NC
NC
V
OUT
TYPICAL APPLICATION
CIRCUIT
V
BYP
GND
IN
IN
TC1268
ERROR
SHDN
V
Regulated voltage output.
Ground terminal.
No connect.
Reference bypass input. Connecting a 470pF to this input further reduces output noise.
Out-of-Regulation Flag. (Open drain output). This output goes low when V
by approximately -5%.
Shutdown control input. The regulator is fully enabled when a logic high is applied to this input.
The regulator enters shutdown when a logic low is applied to this input. During shutdown, output
voltage falls to zero and supply current is reduced to 5µA (typical).
No connect.
Unregulated supply input.
WK
OUT
. The Wake-up Time
C1
+
WK
SHDN
+
C
1µF
) and Settling
0.2µF
OUT
V
OUT
OFF
V
+
ON
R1
1M
OUT
The total turn on response is defined as the Settling
Time (T
T
within 2% of its fully enabled value (15µsec typical)
when released from shutdown. The settling time of the
output voltage is dependent on load conditions and
output capacitance on V
The Wake-up Time (T
to consider when using the TC1268 in RAMBUS
applications. In this application, the bus voltage is held
at 2.5V by a switching regulator during normal power
conditions and can be switched to low power mode,
where the TC1268 takes over and supplies the same
2.5V, but at a much lower current (300mA). In order to
not see the bus voltage drop during the transition from
high power to low power, the TC1268 has a very fast
wake-up time of 5µsec to support the 2.5V rail. This
makes the TC1268 ideal for applications involving
RAMBUS.
FIGURE 3-2:
WK
SHDN
V
OUT
) is defined as the condition when the output is
Description
S
), see Figure 3-2. Settling Time (inclusive with
V
IL
TIME
WAKE-UP RESPONSE
WK
©
OUT
) is an important parameter
2002 Microchip Technology Inc.
(RC response).
OUT
2%
is out-of-tolerance
T
WK
V
98%
IH
T
S