LTC2915IDDB1#PBF Linear Technology, LTC2915IDDB1#PBF Datasheet - Page 9

• Manufacturer Part Number: LTC2915IDDB1#PBF
• Manufacturer: Linear Technology

Specifications of LTC2915IDDB1#PBF

• Operating Supply Voltage (min): 1.5V
• Operating Supply Voltage (max): 5.5V
• Operating Temperature Classification: Industrial
• Operating Temp Range: -40C to 85C
• Pin Count: 8
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

Typically, the user will pick a value of R1 based on accept-
able current draw. Current used by the resistor divider will
be approximately
Recommended range of R1 is 1k to 1M. Higher values
of resistance exacerbate the degradation of threshold
accuracy due to leakage currents.
If the nominal value of the supply being monitored is
V
Resistor tolerances must be taken into account when
determining the overall accuracy.
Selecting the Reset Timing Capacitor
The reset timeout period can be set to one of two fi xed
internal timers or set with a capacitor in order to accom-
modate a variety of applications. Connecting a capacitor,
C
period, t
of capacitor needed for a particular timeout:
For example, using a standard capacitor value of 2.2nF
would give 20ms delay.
Figure 2 shows the reset timeout period as a function of
the value of the timer capacitor.
APPLICATIONS INFORMATION
NOM
RT
R2 = R1(2V
C
R
, between the RT pin and ground sets the reset timeout
RT
1
, then
=
Figure 2. Reset Timeout Period vs RT Capacitance
= t
⎛
⎝ ⎜
RST
10000
0 5
RST
1000
100
.
0.1
. The following formula approximates the value
10
I
0.001
1
V
• 110 [pF/ms]
⎞
⎠ ⎟
NOM
0.01
RT PIN CAPACITANCE, C
– 1)
0.1
1
10
RT
(nF)
100
29156 F02
1000
Leaving RT open with no external capacitor generates a
reset timeout of approximately 400μs. Shorting RT to V
generates a reset timeout of approximately 200ms.
RST Output Characteristics
The DC characteristics of the RST pull-down strength
are shown in the Typical Performance Characteristics
section. RST is an open-drain pin and thus requires an
external pull-up resistor to the logic supply. RST may be
pulled above V
are observed.
The open-drain of the RST pin allows for wired-OR con-
nection of several LTC2915/LTC2916s.
As noted in the discussion of power up and power down,
the circuits that drive RST are powered by V
fault condition, V
low.
Manual Reset (LTC2916 Only)
The LTC2916 includes the MR pin for applications where
a manual reset is desired. MR is internally pulled up, al-
lowing it to interface with a push button with no external
components required. Asserting MR low when RST is high,
initiates a reset, resulting in RST being asserted low for
the set reset timeout.
Shunt Regulator
The LTC2915 and LTC2916 contain an internal 6.2V shunt
regulator on the V
voltage supply. To operate the part from a supply higher
than 5.7V, the V
the supply. This resistor should be sized according to the
following equation:
where V
and maximum of the supply.
As an example, consider operation from an automobile
battery which might dip as low as 10V or spike to 60V. We
must then pick a resistance between 10.86k and 12k.
V
S MAX
(
S(MIN)
5
mA
)
−
5 7
.
CC
and V
CC
V
CC
, providing the voltage limits of the pin
pin must have a series resistor, R
CC
≤
of at least 1V ensures that RST pulls
LTC2915/LTC2916
R
S(MAX)
pin to allow operation from a high
CC
≤
V
are the operating minimum
S MIN
(
250μ
)
−
A
7
V
CC
. During a
CC
29156fa
9
, to
CC