The MAX1887/MAX1897 step-down slave controllers are intended for low-voltage, high-current, multiphase DC-to-DC applications. The MAX1887/MAX1897 slave controllers can be combined with any of Maxim's Quick-PWM™ step-down controllers to form a multiphase DC-to-DC converter. Existing Quick-PWM controllers, such as the MAX1718, function as the master controller, providing accurate output voltage regulation, fast transient response, and fault protection features. Synchronized to the master's low-side gate driver, the MAX1887/MAX1897 include the Quick-PWM constant on-time controller, gate drivers for a synchronous rectifier, active current balancing, and precision current-limit circuitry.
The MAX1887/MAX1897 provide the same high efficiency, ultra-low duty factor capability, and excellent transient response as other Quick-PWM controllers. The MAX1887/MAX1897 differentially sense the inductor currents of both the master and the slave across current-sense resistors. These differential inputs and the adjustable current-limit threshold derived from an external reference allow the slave controller to accurately balance the inductor currents and provide precise current-limit protection. The MAX1887/MAX1897's dual-purpose current-limit input also allows the slave controller to automatically enter a low-power standby mode when the master controller shuts down.
The MAX1887 triggers on the rising edge of the master's low-side gate driver, which staggers the on-times of both master and slave, providing out-of-phase operation that can reduce the input ripple current and consequently the number of input capacitors. The MAX1897 features a selectable trigger polarity, allowing out-of-phase or simultaneous in-phase operation.
Key Features
Applications/Uses
Quick-PWM Slave Controller
Precise, Active Current Balance (±1.25mV)
Accurate, Adjustable Current-Limit Threshold
Optimized for Low-Output Voltages (≤ 2V)
4V to 28V Battery Input Range
Fixed 300kHz (MAX1887) or Selectable 200kHz/300kHz/550kHz (MAX1897) Switching Frequency
Drive Large Synchronous-Rectifier MOSFETs
525µA (typ) ICC Supply Current
20µA Standby Supply Current
< 1µA Shutdown (MAX1897) Supply Current
Small 16-Pin QSOP (MAX1887), Compact 20-Pin 5mm x 5mm QFN (MAX1897), or 20-Pin 5mm x 5mm Thin QFN (MAX1897)
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 prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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