The MAX8520/MAX8521 is designed to drive thermoelectric coolers (tec) in space-confined optical modules. Both devices provide ±1.5A output current and control TEC current to eliminate harmful electrical surges. On-chip FETs reduce external components, and the high switching frequency reduces the size of external components.
Typical Operating Circuit
The MAX8520/MAX8521 runs from a single power supply and bias the TEC between the outputs of two synchronous step-down regulators. This operation allows no "dead zone" or other nonlinear temperature control at low current. This arrangement ensures that the control system does not hunt when the set point is very close to its natural operating point, requiring only a small amount of heating or cooling.
Functional diagram of current control loop
Analog control signals precisely set the TEC current. Both devices have precise, individually adjustable heating and cooling limits as well as maximum TEC voltage limits to improve the reliability of the optical module.The analog output signal is used to monitor TEC current. A unique ripple cancellation program helps reduce noise.
The MAX8520 comes in a 5mm x 5mm TQFN package, whose switching frequency can be adjusted to 1MHz using an external resistor. The MAX8521 is also available in 5mm x 5mm TQFN as well as space-saving 3mm x 3mm UCSP™ and 36-bump WLP (3mm x 3mm) packages with a 500kHz or 1MHz pin optional switching frequency.
Functional Diagram
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