The 22-channel multiple switch detection interface detects opening and closing of switch contacts and reports status to an MCU over SPI. It supports 14 switch-to-ground inputs and 8 programmable switch inputs with selectable wetting current levels from 2 mA to 20 mA. The device operates from a 4.5 V to 36 V battery supply, with full parametric operation from 6.0 V to 28 V and a 3.0 V to 5.25 V logic supply. A 24-to-1 analog multiplexer provides buffered access to switch inputs, battery sensing, and die temperature monitoring.
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| Switch detection channels | 22 |
| Switch-to-ground inputs | 14 |
| Programmable switch inputs | 8 |
| Battery supply operating voltage | 4.5 to 36V |
| Full parametric battery voltage range | 6.0 to 28V |
| Logic supply voltage | 3.0 to 5.25V |
| Switch input voltage range | -1.0 to 36V |
| Selectable wetting current | 2, 6, 8, 10, 12, 14, 16, 20mA |
| Low-power mode battery current | 40 maxµA |
| Logic low-power mode current | 10 maxµA |
| Normal mode battery supply current | 12 maxmA |
| Analog multiplexer ratio | 24:1 |
| SPI transfer frequency | 8 maxMHz |
| Ambient operating temperature | -40 to 125°C |
| Junction operating temperature | -40 to 150°C |
| Battery voltage maximum rating | -0.3 to 40V |
| Supply voltage maximum rating | -0.3 to 7.0V |
| Human body model ESD voltage | ±2000 to ±4000 depending on variant and pinV |
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These are design resources that include the NXP MC33978
User guide for NXP KIT33978EKEVB evaluation boards featuring the MC33978 22-channel switch detection interface with programmable wetting current and SPI connectivity.
