LTC1235CS Linear Technology, LTC1235CS Datasheet - Page 8

• Manufacturer Part Number: LTC1235CS
• Manufacturer: Linear Technology

Specifications of LTC1235CS

• 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: Yes
• Package Type: SOL
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.5V
• Reset Threshold Voltage (max): 4.75V
• Reset Threshold Voltage (min): 4.5V
• 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: Not Compliant

LTC1235
APPLICATIONS INFORMATION
Power Monitoring
The LTC1235 uses a bandgap voltage reference and a
precision voltage comparator C1 to monitor the 5V supply
input on V
the reset voltage threshold, the reset outputs are forced
to active states. The reset voltage threshold accounts for
a 5% variation on V
when V
the reset signals are held active states for a minimum
of 140ms after the reset voltage threshold is reached to
allow the power supply and microprocessor to stabilize.
On power-down, the RESET signal remains active low
even with V
the microprocessor in stable shutdown condition. Figure
1 shows the timing diagram of the RESET signal.
The precision voltage comparator, C1, typically has 40mV
of hysteresis which ensures that glitches at V
activate the reset outputs. Response time is typically 10μs.
8
CC
falls below 4.75V (4.65V typical). On power-up,
CC
CC
(see Block Diagram). When V
as low as 1V. This capability helps hold
LOW LINE
RESET
CC
V
CC
, so the reset outputs become active
V
PB RST
RESET
RESET
CC
= 5V
V2
t1
CC
CC
LOGIC LOW
falls below
Figure 1. Reset Active Time
pin do not
Figure 2. Push-Button Reset
t1
t1 = PUSH-BUTTON RESET LOW TIME
t2 = RESET ACTIVE TIME
V1
V2
To help prevent mistriggering due to transient loads, V
pin should be bypassed with a 0.1μF capacitor with the
leads trimmed as short as possible.
LOW LINE is the output of the precision voltage compara-
tor C1. When V
LOW LINE goes low. LOW LINE returns high as soon as
V
Push-Button Reset
The LTC1235 provides an logic input pin for direct con-
nection to a push-button. The push-button reset input,
PB RST, requires an active low signal. Internally, this input
signal is debounced and timed for a minimum of 40ms.
When this condition is satisfi ed, the reset pulse generator
forces the reset outputs to active states. The reset signals
will remain in active states for a minimum of 140ms from
the moment the push-button reset input is released from
logic low level (Figure 2).
CC
LOGIC
HIGH
rises above the reset voltage threshold.
t1 = RESET ACTIVE TIME
V1 = RESET VOLTAGE THRESHOLD
V2 = RESET VOLTAGE THRESHOLD +
RESET THRESHOLD HYSTERESIS
t1
LOGIC HIGH
LOGIC LOW
t2
CC
falls below the reset voltage threshold,
1235 F02
V1
1235 F01
1235fa
CC