ADGM1004JCPZ-R2 datasheet(25/32 Pages) AD

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Data Sheet

ADGM1004

Rev. D | Page 25 of 32

Hardware Reset

The digital section of the ADGM1004 goes through an

initialization phase during VDD power-up. To hardware reset the

device, power cycle the VDD input. After power-up or a hardware

reset, ensure that there is a minimum of 10 μs from the time of

power-up or reset before any SPI command is issued. Ensure that

VDD does not drop out during the 10 μs initialization phase because

VDD dropout can result in incorrect operation of the ADGM1004.

Internal Error Status

When an internal error is detected in the device, the internal

error is flagged by the INTERNAL_ERROR bits (Bits[7:6]) of

the SWITCH_DATA register (Register 0x20), as shown in Table 9.

An internal error results from an error in the configuration of

the device at power up.

INTERNAL OSCILLATOR FEEDTHROUGH

The ADGM1004 has an internal oscillator running at a nominal

10 MHz. This oscillator drives the charge pump circuitry that

provides the actuation voltage for each switch gate electrode.

Although this oscillator is low power, the 10 MHz signal is

coupled to the switch and is considered a noise spur on the

switch channels. The magnitude of this feedthrough noise spur is

specified in Table 1 and is typically −123 dBm or −146 dBm/Hz

when one switch is on. When all four switches are simultaneously

on, the feedthrough goes up to −120 dBm. VDD level and

temperature changes affect the frequency of the noise spur. For

the maximum and minimum frequency range over temperature

and voltage supply range, see Table 1.

INTERNAL OSCILLATOR FEEDTHROUGH

MITIGATION

In normal operation, the 80 V actuation voltage is supplied by

the driver IC. Setting the EXTD_EN pin low enables the built in

10 MHz oscillator. This setting enables the charge pump circuitry

to generate the 80 V required for MEMS switch actuation. The

internal oscillator is a source of noise that couples through to

the RF ports. The magnitude of this feedthrough noise spur is

specified in Table 1 and is typically −123 dBm or −146 dBm/Hz

when one switch is on. To eliminate the internal oscillator

feedthrough, set the EXTD_EN pin high to disable the internal

oscillator and charge pump circuitry. When the internal oscillator

and charge pump circuitry is disabled, the VCP pin must be

driven with 80 V dc (VCPEXT) from an external voltage supply

required for MEMS switch actuation, as shown in Table 5. The

switch can still be controlled via the digital logic interface pins.

LOW POWER MODE

Setting the EXTD_EN pin high shuts down the internal

oscillator. The ADGM1004 enters a low power quiescent state,

drawing only 50 μA maximum supply current.

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