LTC2908CDDB-B1#TR Linear Technology, LTC2908CDDB-B1#TR Datasheet - Page 13

• Manufacturer Part Number: LTC2908CDDB-B1#TR
• Description: IC MONITOR SIX SUPPLY PREC 8DFN
• Manufacturer: Linear Technology
• Type: Multi-Voltage Supervisorr

Specifications of LTC2908CDDB-B1#TR

• Number Of Voltages Monitored: 6
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 160 ms Minimum
• Voltage - Threshold: 1.403V, 1.683V, 2.338V, 3.086V, Adj, Adj
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-DFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
RST Output Characteristics
The DC characteristics of the RST pull-up and pull-down
strength are shown in the Typical Performance Character-
istics section. The RST output has a weak internal pull-up
to V
The weak pull-up and strong pull-down arrangement allows
this pin to have open-drain behavior while possessing
several other benefi cial characteristics.
The weak pull-up eliminates the need for external pull-up
resistors when the rise time on these pins is not critical.
On the other hand, the open-drain RST behavior allows for
wired-OR connections and can be useful when more than
one signal needs to pull down on the RST line.
As noted in the discussion of power-up and power-down,
the circuits that drive RST are powered by V
a fault condition, a V
maximum V
Output Rise and Fall Time Estimation
The following formula estimates the output fall time (90% to
10%) for a particular external load capacitance (C
where R
TYPICAL APPLICATIONS
t
FALL
CC
= Max(V1, V2) and a strong pull-down to ground.
≈ 2.2 • R
PD
OL
is the on-resistance of the internal pull-
= 0.15V at RST.
PD
• C
CC
LOAD
of at least 0.5V guarantees a
Six Supply Monitor, 5% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1V
DC/DC
DC/DC
DC/DC
DC/DC
DC/DC
12V
5V
3.3V
2.5V
1.8V
1.0V
V1
CC
0.1μF
C1
. During
LOAD
0.1μF
C2
V2 V3 V4
):
LTC2908-A1
GND
2.15M
down transistor estimated to be typically 40Ω at room
temperature (25°C) and C
capacitance on the pin. Assuming a 150pF load capacitance,
the fall time is about 13ns.
The rise time on the RST pin is limited by a weak internal
pull-up current source to V
mates the output rise time (10% to 90%) at the RST pin:
where R
tor. Notice that this pull-up transistor is modeled as a
6μA current source in the Block Diagram as a typical
representation.
The on-resistance as a function of the V
voltage (for V
as follows:
At V
capacitance, the rise time is 86μs. A smaller external
pull-up resistor may be used if the output needs to pull
up faster and/or to a higher voltage. For example, the rise
time reduces to 3.3μs for a 150pF load capacitance when
using a 10k pull-up resistor.
R1
V
t
R
ADJ1
RISE
CC
PU
100k
R2
= 3.3V, R
=
≈ 2.2 • R
PU
86.6k
MAX V1,V2
R3
V
is the on-resistance of the pull-up transis-
ADJ2
RST
CC
100k
(
6 • 10
R4
> 1V) at room temperature is estimated
PU
PU
2908 TA02
is about 260k. Using 150pF for load
• C
SYSTEM
5
)
LOAD
– 1V
CC
Ω
LOAD
. The following formula esti-
is the external load
LTC2908
CC
= Max(V1, V2)
13
2908fd