There are two versions: NMUX1308, an 8:1 analogue multiplexer/demultiplexer which is compatible with, but more capable than, existing 4851 and 4051 analogue switches, and the NMUX1309 dual 4:1 analogue mux/demux which can replace 4852 and 4052 devices.
All analogue signal paths are bidirectional, and automotive-qualified (-40 to +125°C) AEC-Q100 qualified automotive variants will be available – with an automated optical inspection compatible package option. Standard version operate across -40 to +85°C.
Analogue inputs
Like the 48xx versions, the new parts implement ‘injection current control’ on analogue input/outputs that are nominally ‘off”, prevent spikes and signals just above Vcc or just below 0V from forcing current flow and corrupting channels that are nominally ‘on’.
“This integration makes the use of external over-voltage clamp components, a resistive diode network for example, unnecessary, said the company.
That said, analogue ports are shunted to ground via internal FETs if switch voltage is pushed above Vcc (or below ground) – positive clamping starts somewhere above Vcc + 0.5V.
On top of this “a power-off protection feature allows analogue pins to be biased prior to system power-up and to remain biased after system power-down”, said Nexperia. “This removes the restrictions associated with power sequencing and ADC circuitry further down the signal-chain.”
The data sheet rRev 1.1)does not describe this power-off protection in detail – Electronics Weekly has asked for further information.
Digital inputs
The logic input thresholds are largely independent of supply voltage. If the supply is adjusted from 1.8 to 5V, the low-end of the high threshold varies from 0.99 t0 1.32V, while the high-end of the low threshold varies from 530mV to 790mV.
Digital input ESD protection does not have a connection path to Vcc, allowing 6V abs max to be applied regardless of Vcc value.
Once again, according to the company, fail-safe logic allows the digital control inputs to be biased prior to system power-up and remain to biased after the system has powered down – removing the need for power rail sequencing between the analogue switch and the host MCU.
Analogue and digital clamps offer protection, but are not magical. Analogue port current needs to be limited externally if it could be forced above ±50mA (±25mA above 85°C), while for digital inputs the figure is ±30mA could be forced through a digital input. The related figure for the ground pin from any combination of analogue or digital inputs is ±100mA.
Product pages:
NMUX1308 single 8:1 analogue mux/demux
NMUX1309 dual 4:1 analogue mux/demux
