LTC695CSW-3.3#PBF Linear Technology, LTC695CSW-3.3#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC695CSW-3.3#PBF
• Description: IC MPU SUPRVSRY CIRC 3.3V 16SOIC
• Manufacturer: Linear Technology
• Type: Simple Reset/Power-On Resetr

Specifications of LTC695CSW-3.3#PBF

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active High/Active Low
• Reset Timeout: 140 ms Minimum
• Voltage - Threshold: 2.9V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC694-3.3/LTC695-3.3
The LTC694-3.3/LTC695-3.3 are protected for safe area
operation with short-circuit limit. Output current is limited
to approximately 200mA. If the device is overloaded for
a long period of time, thermal shutdown turns the power
switch off until the device cools down. The threshold
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 LTC694-3.3/LTC695-3.3 use 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.
10
BATT
BATT
Figure 2. Using BATT ON to Drive External PNP Transistor
pin in competitive devices and adds to the charging
pin is strictly junction leakage.
3.3V
2.4V
ANY PNP POWER TRANSISTOR
0.1μF
3
1
V
V
BATT
CC
LTC695-3.3
BATT ON
GND
4
5
V
OUT
2
BATT
0.1μF
694/5-3.3 F02
input to V
OUT
The operating voltage at the V
to 2.75V. The charging resistor for 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 the 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
operation. The leakage current then charges up the V
pin again 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 so the external resistor
required to hold V
With V
this resistor will draw only 0.7μA from the battery, which
is negligible in most cases.
CC
OUT
R ≤
, the LTC694-3.3/LTC695-3.3 switch to battery backup.
CC
pulls V
CC
Figure 3. Charging External Battery Through V
(Figure 3).
BATT
V
3.3V
CC
= 3V, a 2.7M resistor will work. With a 2V battery,
0.1μF
1µA
– 50mV
to GND will hold the pin low while changing
BATT
2.4V
low and the device goes back to normal
BATT
below V
I =
V
V
BATT
CC
LTC694-3.3
LTC695-3.3
V
OUT
GND
OUT
R
BATT
– V
R
V
BATT
OUT
CC
BATT
since this eliminates the
reaches within 50mV of
BATT
is:
pin ranges from 1.5V
694/5-3.3 F03
pin. The oscillation
0.1μF
OUT
69453fb
BATT