LTC2908CDDB-B1#TRMPBF Linear Technology, LTC2908CDDB-B1#TRMPBF Datasheet - Page 11

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

Specifications of LTC2908CDDB-B1#TRMPBF

• 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: Lead free / RoHS Compliant
• Other names: LTC2908CDDB-B1#PBF; LTC2908CDDB-B1#PBF

APPLICATIONS INFORMATION
Adjustable Input
The noninverting input on the V
0.5V. And the high impedance inverting input directly ties
to the V
In a typical application, this pin connects to a tap point on an
external resistive divider between the positive voltage being
monitored and ground (see Figure 3). The following formula
derives the value of the R1 resistor in the divider from a
particular value of R2 and the desired trip voltage:
R2 = 100k is recommended. Table 1 shows suggested
1% resistor values for various adjustable applications and
their corresponding trip thresholds.
Table 1. Suggested 1% Resistor Values for the V
V
R1=
SUPPLY
7.5
3.3
2.5
1.8
1.5
1.2
1.0
0.9
0.8
0.7
0.6
12
10
8
6
5
3
ADJ
V
(V)
0.5V
Figure 3. Setting the Adjustable Trip Point
TRIP
pin.
V
ADJ
V
– 1 R2
TRIP
R1
1%
R2
1%
V
TRIP
11.25
4.725
3.055
2.325
1.685
1.410
1.120
0.933
0.840
0.750
0.655
0.561
2.82
9.4
7.5
5.6
7
(V)
LTC2908-A1/LTC2908-B1/LTC2908-C1
+
–
0.5V
–
+
ADJ
R1 (kΩ)
2150
1780
1400
1300
1020
86.6
68.1
49.9
30.9
12.1
845
511
464
365
237
182
124
comparator is set to
2908 F03
ADJ
Inputs
R2 (kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
In an application with less than six supply voltages, the
unused supervisor inputs should be tied to the closest
higher supply voltage available.
Threshold Accuracy
Specifying system voltage margin for worst-case operation
requires the consideration of three factors: power supply
tolerance, IC supply voltage tolerance and supervisor reset
threshold accuracy. Highly accurate supervisors ease the
design challenge by decreasing the overall voltage margin
required for reliable system operation.
Consider a 5V system with a ±5% power supply tolerance
band. System ICs powered by this supply must operate
reliably within this band (and a little more, as explained
below). The bottom of the supply tolerance band, at 4.75V
(5% below 5V), is the exact voltage at which a perfectly
accurate supervisor generates a reset (see Figure 4).
Such a perfectly accurate supervisor does not exist—the
actual reset threshold may vary over a specifi ed band
(±1.5% for the LTC2908 supervisors). Figure 5 shows
the typical relative threshold accuracy for all six inputs
overtemperature.
THRESHOLD
Figure 5. Typical Threshold Accuracy vs Temperature
±1.5%
BAND
5.000V
4.750V
4.675V
4.600V
4.500V
Figure 4. Threshold Band Diagram
–0.5
–1.0
–1.5
1.5
1.0
0.5
0
–50
MINIMUM
RELIABLE
REGION OF POTENTIAL MALFUNCTION
VOLTAGE
SYSTEM
–25
WITH 2.5% MONITOR
TOLERANCE
TEMPERATURE (°C)
SUPPLY
0
25
SUPERVISOR
THRESHOLD
50
IDEAL
2908 F04
75
2908 F05
LTC2908
–5.0%
–6.5%
–8.0%
–10%
NOMINAL
VOLTAGE
SUPPLY
100
±2.5%
THRESHOLD
BAND
11
2908fd