+3.3V/+5V, 8-Channel, Cascadable Relay Drivers with Serial/Parallel Interface

8-Channel, +3V/+5V, Cascadable Relay Drivers with Serial/Parallel Interface

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The MAX4820/MAX4821 8-channel relay drivers offer built-in kickback protection and drive +3.3V/+5V nonlatching or dual-coil-latching relays. These devices are especially useful when driving +3V relays. Each independent open-drain output features a 2Ω on-resistance and is guaranteed to sink 70mA (min) of load current. Both devices consume less than 50µA (max) quiescent current and have 1µA output off-leakage current.

The MAX4820 features an SPI™-/QSPI™-/MICROWIRE™-compatible serial interface. Input data is shifted into an 8-bit shift register and latched to the outputs when active-low CS transitions from low to high. Each data bit in the shift register corresponds to a specific output, allowing independent control of all outputs.

The MAX4821 features a 4-bit (A0, A1, A2, LVL) parallel-input interface. The first three bits (A0, A1, A2) determine the output address, and the fourth bit (LVL) determines whether the selected output is switched on or off. Data is latched to the outputs when active-low CS transitions from low to high.

Both devices feature separate set and reset functions that allow the user to turn on or turn off all outputs simultaneously with a single control line. Built-in hysteresis (Schmidt trigger) on all digital inputs allows these devices to be used with slow rising and falling signals, such as those from optocouplers or RC power-up initialization circuits. The MAX4820/MAX4821 are available in 20-pin TSSOP and space-saving 20-pin thin QFN packages.
MAX4820, MAX4821: Typical Application Circuits MAX4820, MAX4821: Typical Application Circuits Enlarge+

Key Features

  • 8 Independent Output Channels
  • Built-In Inductive Kickback Protection
  • Drive +3V and +5V Relays
  • Guaranteed 70mA (min) Coil Drive Current
  • Active-Low SET Function to Turn On All Outputs Simultaneously
  • Active-Low RESET Function to Turn Off All Outputs Simultaneously
  • SPI-/QSPI-/MICROWIRE-Compatible Serial Interface (MAX4820)
  • Serial Digital Output for Daisy Chaining (MAX4820)
  • Parallel Interface (MAX4821)
  • Low 50µA (max) Quiescent Supply Current
  • Space-Saving 20-Pin Thin QFN Package


  • Automated Test Equipment (ATE)
  • Central Office
  • DSL, ADSL Line Cards
  • E1/T1 Redundancy
  • Industrial Equipment

See parametric specs for Relay Drivers (6)

Part NumberISOURCE @2.7V
RON @2.7V
guar. minmaxmaxSee Notes
MAX4820 706508SPI2.3 to 5.5
$1.90 @1k
MAX4821 Parallel

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Technical Documents

App Note 4653 FAQs about Analog Switches
App Note 3288 IC Drives Up to Four Single-Coil Latching Relays

Tools & Models

  • MAX4820 IBIS Model
  • Product Reliability Reports: MAX4820.pdf 
    Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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