LTC695CSW#PBF Linear Technology, LTC695CSW#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC695CSW#PBF
• Description: IC MPU SUPERVISRY CIRCUIT 16SOIC
• Manufacturer: Linear Technology
• Type: Simple Reset/Power-On Resetr

Specifications of LTC695CSW#PBF

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active High/Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 4.65V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Number Of Elements: 1
• Monitored Voltage 1 (typ): 4.65V
• Battery Backup Switching: Yes
• Watchdog Timer: Yes
• Chip Enable Signals: Yes
• Reset Active Time: 280ms
• Manual Reset: No
• Package Type: SOIC W
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.5V
• Reset Threshold Voltage (max): 4.75V
• Reset Threshold Voltage (min): 4.5V
• Family Name: LTC695
• Power Dissipation: 500mW
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Power Fail Detection: Yes
• Mounting: Surface Mount
• Pin Count: 16
• Supply Current: 1.5mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC690/LTC691
LTC694/LTC695
APPLICATIONS INFORMATION
external PNP transistor (Figure 2). If higher currents
are needed with the LTC690 and LTC694, a high current
Schottky diode can be connected from the V
V
The LTC690 family is protected for safe area operation
with short-circuit limit. Output current is limited to
approximately 200mA. If the device is overloaded for
long period of time, thermal shutdown turns the power
switch off until the device cools down. The threshhold
temperature for thermal shutdown is approximately 155°C
with about 10°C of hysteresis which prevents the device
from oscillating in and out of shutdown.
The PNP switch used in competitive devices was not chosen
for the internal power switch because it injects unwanted
current into the substrate. This current is collected by the
V
current of the battery which can damage lithium batteries.
The LTC690 family uses a charge pumped NMOS power
switch to eliminate unwanted charging current while
achieving low dropout and low supply current. Since no
current goes to the substrate, the current collected by
V
A 125Ω PMOS switch connects the V
in battery back-up mode. The switch is designed for very
low dropout voltage (input-to-output differential). This
feature is advantageous for low current applications such
as battery back-up in CMOS RAM and other low power
CMOS circuitry. The supply current in battery back-up
mode is 1μA maximum.
The operating voltage at the V
to 4.25V. High value capacitors, such as electrolytic or
10
OUT
BATT
BATT
Figure 2. Using BATT ON to Drive External PNP Transistor
pin to supply the extra current.
pin in competitive devices and adds to the charging
pin is strictly junction leakage.
5V
0.1μF
3V
ANY PNP POWER TRANSISTOR
3
1
V
V
BATT
CC
BATT ON
LTC691
LTC695
GND
4
5
BATT
V
OUT
pin ranges from 2.0V
2
BATT
0.1μF
690 F02
input to V
CC
pin to the
OUT
farad-size double layer capacitors, can be used for short
term memory back-up instead of a battery. The charging
resistor for both capacitors and rechargeable batteries
should be connected to V
discharge path that exists when the resistor is connected
to V
Replacing the Back-Up Battery
When changing the back-up battery with system power
on, spurious resets can occur while battery is removed
due to battery standby current. Although battery standby
current is only a tiny leakage current, it can still charge
up the stray capacitance on the V
cycle is as follows: When V
V
V
The leakage current then charges up the V
and the cycle repeats.
If spurious resets during battery replacement pose no
problems, then no action is required. Otherwise, a resistor
from V
the battery. For example, the battery standby current is
1μA maximum over temperature and the external resistor
required to hold V
With V
battery, this resistor will draw only 0.7μA from the battery,
which is negligible in most cases.
CC
BATT
R
, the LTC690 switches to battery back-up. V
CC
≤
low and the device goes back to normal operation.
Figure 3. Charging External Battery Through V
V –50mV
(Figure 3).
BATT
CC
CC
5V
= 4.5V, a 4.3M resistor will work. With a 3V
1 A
0.1μF
to GND will hold the pin low while changing
μ
3V
BATT
below V
I =
V
V
CC
BATT
V
OUT
LTC690
LTC691
LTC694
LTC695
OUT
GND
BATT
R
– V
R
V
OUT
CC
BATT
since this eliminates the
reaches within 50mV of
BATT
is:
pin. The oscillation
690 F03
0.1μF
BATT
OUT
pin again
OUT
pulls
690fe