CS8151C Cherry Semiconductor Corporation, CS8151C Datasheet - Page 5

• Manufacturer Part Number: CS8151C
• Description: 5V/ 100mA Low Dropout Linear Regulator with Watchdog/ RESET/ & Wake Up
• Manufacturer: Cherry Semiconductor Corporation

To reduce the drain on the battery a system can go into a
low current consumption mode when ever its not per-
forming a main routine. The Wake Up signal is generated
continuously and is used to interrupt a microcontroller
that is in sleep mode. The nominal output is a 5 volt
square wave with a duty cycle of 50% at a frequency that
is determined by a timing capacitor, C
When the microprocessor receives a rising edge from the
Wake Up output, it must issue a watchdog pulse and
check its inputs to decide if it should resume normal oper-
ations or remain in the sleep mode.
The first falling edge of the watchdog signal causes the
Wake Up to go low within 2µs (typ) and remain low until
the next Wake Up cycle (see Figure 2). Other watchdog
pulses received within the same cycle are ignored (Figure
1).
During power up,
age is in regulation. During operation, if the output volt-
age shifts below the regulation limits, the RESET toggles
low and remains low until proper output voltage regula-
tion is restored. After the
high.
The Watchdog circuitry continuously monitors the input
watchdog signal (WDI) from the microprocessor. The
absence of a falling edge on the Watchdog input during
one Wake Up cycle will cause a
the end of the Wake Up cycle. (see Figure 1b).
The Wake Up output is pulled low during a
regardless of the cause of the
returns high, the Wake Up cycle begins again (see Figures
1b).
The
external capacitor C
Wake Up period=(4x10
Dropout Voltage:
Input Voltage:
Line Regulation:
RESET
RESET
RESET
RESET
The input-output voltage differential at which the cir-
cuit ceases to regulate against further reduction in
input voltage. Measured when the output voltage has
dropped 100mV from the nominal value obtained at
14V input, dropout voltage is dependent upon load
current and junction temperature.
The DC voltage applied to the input terminals with
respect to ground.
The change in output voltage for a change in the
input voltage. The measurement is made under con-
ditions of low dissipation or by using pulse tech-
niques such that the average chip temperature is not
significantly affected.
high to Wake Up delay time are all set by one
Delay Time=(5x10
HIGH to Wake Up Delay Time =(2x10
pulse width, Wake Up signal frequency and
Functional Description
RESET
Delay
5
.
)C
RESET
is held low until the output volt-
4
Delay
)C
RESET
Delay
RESET
delay,
. After the
Delay
pulse to occur at
RESET
.
RESET
5
returns
)C
RESET
Delay
Definition of Terms
Circuit Description
5
Load Regulation:
Quiescent Current:
Ripple Rejection:
Current Limit:
Capacitor temperature coefficient and tolerance as well as the
tolerance of the CS8151C must be taken into account in order
to get the correct system tolerance for each parameter.
Figure 2. Wake Up response to WDI
Figure 3. Wake Up response to
WAKE UP
WDI
______
RESET
WAKE UP
Peak current that can be delivered to the output.
The change in output voltage for a change in load
current at constant chip temperature.
The part of the positive input current that does not
contribute to the positive load current. The regulator
ground lead current.
The ratio of the peak-to-peak input ripple voltage to
the peak-to-peak output ripple voltage.
Response to
WAKE UP
______
RESET
Response to
WAKE UP
WDI
RESET
(Low Voltage)