ZHCSJM9A April 2019 – September 2019 TPS3840-Q1
PRODUCTION DATA.
This design requires voltage supervision on a 12-V power supply voltage rail with possibility of the 12-V rail rising up as high as 42 V. The undervoltage fault occurs when the power supply voltage drops below 7.7 V.
| PARAMETER | DESIGN REQUIREMENT | DESIGN RESULT |
|---|---|---|
| Power Rail Voltage Supervision | Monitor 12-V power supply for undervoltage condition, trigger a undervoltage fault at 7.7 V. | TPS3840-Q1 provides voltage monitoring with 1% accuracy with device options available in 0.1 V variations. Resistor dividers are calculated based on device variant and desired threshold voltage. |
| Maximum Input Power | Operate with power supply input up to 42 V. | The TPS3840-Q1 limits VDD to 10 V but can monitor voltages higher than the maximum VDD voltage with the use of an external resistor divider. |
| Output logic voltage | Open-Drain Output Topology | Due to large variance in battery voltage, an open-drain output is recommended to provide the correct reset signal. |
| Maximum system current consumption | 35 uA when power supply is at 12 V typical | TPS3840-Q1 requires 350 nA (typical) and the external resistor divider will also consume current. There is a tradeoff between current consumption and voltage monitor accuracy but generally set the resistor divider to consume 100 times current into VDD. |
| Voltage Monitor Accuracy | Typical voltage monitor accuracy of 2.5%. | The TPS3840-Q1 has 1% typical voltage monitor accuracy. By decreasing the ratio of resistor values, the resistor divider will consume more current but the accuracy will increase. The resistor tolerance also needs to be accounted for. |
| Delay when returning from fault condition | RESET delay of at least 200 ms when returning from a undervoltage fault. | CCT = 0.33 µF sets 204 ms delay |