ADGM3144/ADGM3121 MEMS Switch Driver

Supported Devices

• ADGM3144 - SP4T Switch

• ADGM3121 - DPDT Switch

Overview

The ADGM3144 and ADGM3121 are 3mm x 3mm MEMS switches operating from DC to 23 GHz:

• ADGM3144: Single-Pole Four-Throw (SP4T) switch with RF1-4 ports connected to RFC

• ADGM3121: Dual-Pole Dual-Throw (DPDT) switch with RF1A/1B, RF2A/2B ports connected to RFCA/RFCB

This driver supports both devices and control modes:

1. Parallel GPIO Mode: Direct control via IN1-IN4 GPIO pins

2. SPI Mode: Control via SPI interface with register access

Key Features: - DC to 23 GHz frequency range - Low insertion loss: -0.5 dB (typical) at 6 GHz - High isolation: -22 dB (typical) at 6 GHz - Fast switching time: 200 µs (typical) - On resistance: 1.9 Ω (typical) - High cycle count: 100 million cycles minimum at +85°C

Device Configuration

Driver Initialization

The driver supports two operating modes, selected via the PIN/SPI control pin:

Parallel GPIO Mode Example (ADGM3144 SP4T):

struct adgm3121_dev *dev;
struct adgm3121_init_param init_param = {
    .mode = ADGM3121_MODE_PARALLEL,
    .gpio_pin_spi = {
        .number = PIN_SPI_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    },
    .gpio_in1 = {
        .number = IN1_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    },
    .gpio_in2 = {
        .number = IN2_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    },
    .gpio_in3 = {
        .number = IN3_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    },
    .gpio_in4 = {
        .number = IN4_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    }
};

ret = adgm3121_init(&dev, &init_param);

SPI Mode Example (ADGM3121 DPDT):

struct adgm3121_dev *dev;
struct adgm3121_init_param init_param = {
    .mode = ADGM3121_MODE_SPI,
    .gpio_pin_spi = {
        .number = PIN_SPI_GPIO_NUM,
        .platform_ops = &gpio_ops,
        .extra = &gpio_extra
    },
    .spi_init = {
        .device_id = SPI_DEVICE_ID,
        .mode = NO_OS_SPI_MODE_0,
        .bit_order = NO_OS_SPI_BIT_ORDER_MSB_FIRST,
        .max_speed_hz = 10000000, // 10 MHz max
        .chip_select = SPI_CS,
        .platform_ops = &spi_ops,
        .extra = &spi_extra
    }
};

ret = adgm3121_init(&dev, &init_param);

Basic Usage

Individual Switch Control:

// ADGM3144: Enable switch 1 (RF1 to RFC)
// ADGM3121: Enable switch 1 (RF1A to RFCA)
ret = adgm3121_set_switch_state(dev, ADGM3121_SW1, ADGM3121_ENABLE);

// ADGM3144: Disable switch 2 (RF2 to RFC)
// ADGM3121: Disable switch 2 (RF1B to RFCA)
ret = adgm3121_set_switch_state(dev, ADGM3121_SW2, ADGM3121_DISABLE);

// Check switch state
enum adgm3121_state state;
ret = adgm3121_get_switch_state(dev, ADGM3121_SW1, &state);

Multiple Switch Control:

// Enable switches 1 and 3 simultaneously
ret = adgm3121_set_switches(dev, 0x05); // Binary: 0101

// Get all switch states
uint8_t switch_mask;
ret = adgm3121_get_switches(dev, &switch_mask);

// Reset all switches to off
ret = adgm3121_reset_switches(dev);

SPI Mode Advanced Features

Daisy Chain Mode:

// Enter daisy chain mode for multiple devices
ret = adgm3121_enter_daisy_chain_mode(dev);

// In daisy chain mode, use adgm3121_set_switches() with shift register data

Error Detection:

uint8_t error_status;
ret = adgm3121_check_internal_error(dev, &error_status);
if (error_status != 0) {
    // Handle internal error
    printf("Internal error detected: 0x%02X\\n", error_status);
}

Direct Register Access:

uint8_t switch_data = 0x05; // Enable SW1 and SW3
ret = adgm3121_write_register(dev, ADGM3121_REG_SWITCH_DATA, switch_data);

uint8_t read_data;
ret = adgm3121_read_register(dev, ADGM3121_REG_SWITCH_DATA, &read_data);

Hardware Configuration

Pin Connections:

Pin	ADGM3144	ADGM3121
VDD	3.0V to 3.6V power supply | 3.0V to 3.6V power supply
VCP	80V charge pump output	80V charge pump output
GND	Ground	Ground
RF Ports	RF1-RF4 (SP4T)	RF1A, RF1B, RF2A, RF2B (DPDT)
RFC Port	RFC (common)	RFCA, RFCB (dual common)
PIN/SPI	Mode select (Parallel, SPI)	Mode select (Parallel, SPI)
IN1-IN4	Parallel control pins	Parallel control pins
SDI	SPI data input	SPI data input
SDO	SPI data output	SPI data output
SCLK	SPI clock	SPI clock
CS	SPI chip select	SPI chip select

External Components:

• 0.1 µF decoupling capacitor on VDD (rated ≥16V)

• 0.1 nF decoupling capacitor on VCP (rated ≥100V)

• 50Ω termination on unused RF ports

Performance Specifications

Parameter	Typical	Unit
Frequency Range	DC to 23	GHz
Insertion Loss @ 6GHz	-0.5	dB
Isolation @ 6GHz	-22	dB
Return Loss @ 6GHz	-24.5	dB
On Resistance	1.9	Ω
Switching Time	200	µs
Power-up Time	45	ms
Max RF Power	33	dBm
Max DC Current	200	mA
Cycle Lifetime	100M	cycles

API Reference

Initialization Functions:

• adgm3121_init() - Initialize device

• adgm3121_remove() - Free resources

Switch Control Functions:

• adgm3121_set_switch_state() - Set individual switch state

• adgm3121_get_switch_state() - Get individual switch state

• adgm3121_set_switches() - Set multiple switches with bitmask

• adgm3121_get_switches() - Get all switch states as bitmask

• adgm3121_reset_switches() - Turn off all switches

SPI Mode Functions:

• adgm3121_write_register() - Write to device register

• adgm3121_read_register() - Read from device register

• adgm3121_enter_daisy_chain_mode() - Enable daisy chain mode

• adgm3121_check_internal_error() - Check for internal errors

Troubleshooting

Common Issues:

1. Switch not responding: Check VDD supply (3.0-3.6V) and wait 45ms after power-up

2. SPI communication failure: Verify SPI mode, speed (≤10MHz), and CS timing

3. High insertion loss: Check for proper grounding and 50Ω terminations

4. Internal errors: Use adgm3121_check_internal_error() to diagnose

ESD Precautions:

• RF pins: 150V HBM, 1kV FICDM rating

• Use proper ESD protection during handling

• Avoid hot switching (applying RF power during switching transitions)