LTC2903IS6-A1#PBF Linear Technology, LTC2903IS6-A1#PBF Datasheet - Page 11

• Manufacturer Part Number: LTC2903IS6-A1#PBF
• Manufacturer: Linear Technology

Specifications of LTC2903IS6-A1#PBF

• Voltage Supervisor Type: Voltage Monitor
• Number Of Voltage Supervisors: 4
• Reset Threshold Voltage (max): 2.97/2.25/1.62/AdjV
• Package Type: TSOT-23
• Operating Temperature Classification: Industrial
• Operating Temp Range: -40C to 85C
• Pin Count: 6
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

APPLICATIO S I FOR ATIO
Table 1a contains suggested 1% resistor values for the
ADJ inputs to obtain nominal –11.5% thresholds. Connect
unused supervisor inputs to the highest supply voltage
available.
Table 1a. Suggested 1% Resistor Values for the –11.5% ADJ Inputs
Table 1b contains suggested 1% resistor values for the
ADJ inputs to obtain nominal –6.5% thresholds.
Table 1b. Suggested 1% Resistor Values for the –6.5% ADJ Inputs
V
V
SUPPLY
SUPPLY
7.5
3.3
2.5
1.8
1.5
1.2
0.9
7.5
3.3
2.5
1.8
1.5
1.2
1.0
0.9
0.8
0.7
0.6
12
10
12
10
8
6
5
3
1
8
6
5
3
(V)
(V)
V
V
TRIP
TRIP
U
10.75
4.435
2.935
1.605
1.325
1.065
0.884
0.795
11.25
4.725
3.055
2.325
1.685
1.410
1.120
0.933
0.840
0.750
0.655
0.561
8.95
7.15
5.38
2.66
2.82
6.7
2.2
9.4
7.5
5.6
7
(V)
(V)
U
R1 (kΩ)
R1 (kΩ)
2050
1690
1330
1240
2150
1780
1400
1300
1020
76.8
86.6
68.1
49.9
30.9
12.1
976
787
487
432
340
221
165
113
845
511
464
365
237
182
124
59
W
U
R2(kΩ)
R2(kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Implications of Threshold Accuracy
Specifying system voltage margin for worst-case opera-
tion requires consideration of three factors: power supply
tolerance, IC supply voltage tolerance and supervisor re-
set 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 ±10% 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 4.5V (5V –
10%), is the exact voltage at which a perfectly accurate
supervisor generates a reset. Such a perfectly accurate
supervisor does not exist—the actual reset threshold may
vary over a specified band (±1.5% for the LTC2903-1 su-
pervisors). Figure 4 shows the typical relative threshold
accuracy for all four inputs, over temperature.
With this variation of reset threshold in mind, the nominal
reset threshold of the supervisor resides below the mini-
mum supply voltage, just enough so that the reset thresh-
old band and the power supply tolerance bands do not
overlap. If the two bands overlap, the supervisor could
generate a false or nuisance reset when the power supply
remains within its specified tolerance band (say, at 4.6V).
Adding half of the reset threshold accuracy spread (1.5%)
to the ideal 10% thresholds puts the LTC2903-1 thresh-
olds at 11.5% (typ) below the nominal input voltage. For
example, the 5V typical threshold is 4.425V, or 75mV
below the ideal threshold of 4.500V. The guaranteed
threshold lies in the band between 4.500V and 4.350V
over temperature.
Figure 4. LTC2903 Typical Threshold Accuracy vs Temperature
–1.0
–1.5
–0.5
1.5
0.5
1.0
0
–50
–25
TEMPERATURE (°C)
0
25
50
75
LTC2903-1
29031 F04
100
11
29031f a