SBVS250 April 2015 TPS3779 , TPS3780
PRODUCTION DATA.
The TPS3779 and TPS3780 are used as precision dual-voltage detectors. The monitored voltage, VDD voltage, and output pullup voltage (TPS3780 only) can be independent voltages or connected in any configuration.
Threshold overdrive is how much VDD exceeds the specified threshold, and is important to know because smaller overdrive results in slower OUTx response. Threshold overdrive is calculated as a percent of the threshold in question, as shown in Equation 1:
where
Figure 16 illustrates the VDD minimum detectable pulse versus overdrive, and is used to visualize the relationship overdrive has on tPD(f) for negative-going events.
The resistor divider values and target threshold voltage can be calculated by using Equation 2 and Equation 3 to determine VMON(UV) and VMON(PG), respectively.
where
Choose RTOTAL ( = R1 + R2) so that the current through the divider is approximately 100 times higher than the input current at the SENSEx pins. The resistors can have high values to minimize current consumption as a result of low input bias current without adding significant error to the resistive divider. For details on sizing input resistors, refer to application report SLVA450, Optimizing Resistor Dividers at a Comparator Input, available for download from www.ti.com.
PARAMETER | DESIGN REQUIREMENT | DESIGN RESULT |
---|---|---|
VDD | 5 V | 5 V |
Hysteresis | 10% | 10% |
Monitored voltage 1 | 3.3 V nominal, VMON(PG) = 2.9 V, VMON(UV) = 2.6 V | VMON(PG) = 2.908 V, VMON(UV) = 2.618 V |
Monitored voltage 2 | 3 V nominal, VMON(PG) = 2.6 V, VMON(UV) = 2.4 V | VMON(PG) = 2.606 V, VMON(UV) = 2.371 V |
Output logic voltage | 3.3-V CMOS | 3.3-V CMOS |
PARAMETER | DESIGN REQUIREMENT | DESIGN RESULT |
---|---|---|
VDD | VMON | VMON |
Hysteresis | 10% | 10% |
Monitored voltage 1 | VMON(PG) = 3.3 V, VMON(UV) = 3 V | VMON(PG) = 3.330 V, VMON(UV) = 2.997 V |
Monitored voltage 2 | VMON(PG) = 3.9 V, VMON(UV) = 3.5 V | VMON(PG) = 3.921 V, VMON(UV) = 3.529 V |
where
where