MAX4820, MAX4821

+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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Status Explanations for product status codes

Part Number Status
MAX4820 Active: In Production. See Ordering Information for details.
MAX4821 Active: In Production. See Ordering Information for details.


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.

Data Sheet

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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

Key Specifications:

Relay Drivers
Part Number ISOURCE @2.7V
RON @2.7V
Features Channels Interface VSUPPLY
guar. min max max See Notes
MAX4820  70 6 50
Integrated Kickback Diodes
Power On Reset
Thermal Shutdown
8 SPI 2.3 to 5.5 $1.81 @1k
Integrated Kickback Diodes
Power On Reset
Thermal Shutdown
See All Relay Drivers (7)

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.


MAX4820, MAX4821: Typical Application Circuits
Typical Application Circuits

More Information

New Product Press Release   2004-04-06 ]

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Document Ref.: 19-2751 Rev 2; 2010-02-16
This page last modified: 2010-02-16