LTC2930 Linear Technology, LTC2930 Datasheet - Page 8

• Manufacturer Part Number: LTC2930
• Description: Confi gurable Six Supply Monitor
• Manufacturer: Linear Technology

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Using The Adjustable Thresholds
The reference inputs on the V3 and/or V4 comparators
are set to 0.5V when the positive adjustable modes are
selected (Figure 3). The reference inputs on the V5 and V6
comparators are always set to 0.5V. The tap point on an
external resistive divider, connected between the positive
voltage being sensed and ground, is connected to the high
impedance, adjustable inputs (V3, V4, V5, V6). Calculate
the trip voltage from:
APPLICATIONS INFORMATION
LTC2930
Monitor Confi guration
Select the LTC2930 input voltage combination by placing
the recommended resistive divider from VREF to GND and
connecting the tap point to VPG, as shown in Figure 2.
Table 1 offers recommended 1% resistor values for each
of the 16 modes. The last column in Table 1 specifi es
optimum V
a ratiometric DAC.
At power-up, once V1 or V2 reaches 2.4V, the monitor
enters a setup period of approximately 150μs. During the
setup time, the voltage on the VPG pin is sampled and the
monitor is confi gured to the desired input combination. The
comparators are enabled and supply monitoring begins.
Do not add capacitance to the VPG pin.
8
Figure 3. Setting the Positive Adjustable Trip Point
V3, V4, V5 OR V6
PG
/V
REF
Figure 2. Mode Selection
V
TRIP
LTC2930
ratios (± 0.01), when confi guring with
R3
1%
R4
1%
VREF
GND
VPG
+
–
1%
0.5V
R1
LTC2930
R2
1%
2930 F02
2930 F03
Table 2. Suggested 1% Resistor Values for the ADJ Inputs
*See Figure 3.
Table 3. Suggested 1% Resistor Values for the –ADJ Inputs
*See Figure 4.
In the negative adjustable mode, the reference level on the
V4 comparator is connected to ground (Figure 4). The tap
point on an external resistive divider, connected between
the negative voltage being sensed and the VREF pin, is
V
V
V
SUPPLY
SUPPLY
TRIP
–5.2
–10
–12
7.5
3.3
2.5
1.8
1.5
1.2
0.9
12
10
–2
–5
Figure 4. Setting the Negative Adjustable Trip Point
8
6
5
3
1
(V)
(V)
= 0.5V • 1+
V4
V
TRIP
R4
1%
R3
1%
V
V
–11.30
TRIP
TRIP
–1.87
–4.64
–4.87
–9.31
11.25
4.725
3.055
2.325
1.685
1.410
1.120
0.933
0.840
2.82
9.4
7.5
5.6
7
(V)
(V)
VREF
R3
R4
LTC2930
R3 (kΩ)
R3 (kΩ)
2150
1780
1400
1300
1020
1130
86.6
68.1
187
464
487
931
845
511
464
365
237
182
124
2930 F04
R4 (kΩ)
R4 (kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
121
121
121
121
121
2930fa