LP3470M5-2.75 National Semiconductor, LP3470M5-2.75 Datasheet - Page 6

• Manufacturer Part Number: LP3470M5-2.75
• Description: IC, VOLT SUPERVISOR, 30µA, 5.5V, SOT23-5
• Manufacturer: National Semiconductor

Specifications of LP3470M5-2.75

• Threshold Voltage: 2.75V
• No. Of Supervisors / Monitors: 1
• Supply Voltage Range: 0.5V To 5.5V
• Reset Type: Active-Low
• Supply Current: 30µA
• Delay Time: 1ms
• Digital Ic Case Style: SOT-23
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Information
RESET TIMEOUT PERIOD
The Reset Timeout Period (t
external capacitor (C
Ceramic chip capacitor rated at or above 10V is sufficient. The
Reset Timeout Period (t
lowing formula:
For example a C
delay due to t
should be left floating.
RESET OUTPUT
In applications like microprocessor (µP) systems, errors might
occur in system operation during power-up, power-down, or
brownout conditions. It is imperative to monitor the power
supply voltage in order to prevent these errors from occurring.
The LP3470 asserts a reset signal whenever the V
voltage is below a threshold (V
teed to be a logic low for V
reset threshold, the reset is kept asserted for a time period
(t
terval Reset goes to logic high. If a brownout condition occurs
(monitored voltage falls below the reset threshold minus a
small hysteresis), Reset goes low. When V
Timing Diagram
RP
) programmed by an external capacitor (C
RP
is needed in a certain application, the pin SRT
1
t
RP
of 100 nF will achieve a t
(ms) = 2000 x C
1
) connected to pin SRT of LP3470. A
RP
) can be calculated using the fol-
CC
RP
> 0.5V. Once V
RTH
) is programmable using an
) voltage. Reset is guaran-
1
(µF).
RP
CC
of 200 ms. If no
CC
1
); after this in-
returns above
exceeds the
CC
supply
6
the reset threshold, Reset remains low for a time period t
before going to logic high.
PULL-UP RESISTOR SELECTION
The LP3470's Reset output structure is a simple open-drain
N-channel MOSFET switch. A pull-up resistor (R
connected to V
R
output MOSFET (Q
than 680Ω guarantees this. R
to ensure a logic high while supplying all the leakage current
through the Reset pin. A resistor value of less than 68kΩ sat-
isfies this condition. A typical pull-up resistor value of 20 kΩ
is sufficient in most applications.
NEGATIVE-GOING V
The LP3470 is relatively immune to short duration negative-
going V
acteristics show the Maximum Transient Duration vs. Nega-
tive Transient Amplitude (graph titled Transient Rejection), for
which reset pulses are not generated. This graph shows the
maximum pulse width a negative-going V
typically have without causing a reset pulse to be issued. As
the transient amplitude increases (i.e. goes farther below the
reset threshold), the maximum allowable pulse width de-
creases. A 0.1 µF bypass capacitor mounted close to V
provides additional transient immunity.
1
should be large enough to limit the current through the
CC
transients (glitches). The Typical Operating Char-
CC
.
1
) below 10 mA. A resistor value of more
CC
TRANSIENTS
1
should also be small enough
10001604
CC
transient may
1
) should be
CC
RP