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 ontime 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 dualpurpose 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.
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Notebook Computers CPU Core Supply Single-Stage (BATT to VCORE) Converters Two-Stage (5V to VCORE) Converters Servers/Desktop Computers Telecom
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Quick-PWM Slave ControllerPrecise, Active Current Balance (±1.25mV )Accurate, Adjustable Current-Limit ThresholdOptimized for Low-Output Voltages (2V)4V to 28V Battery Input RangeFixed 300kHz (MAX1887) or Selectable 200kHz/300kHz/550kHz (MAX1897) Switching FrequencyDrive Large Synchronous-Rectifier MOSFETs525µA (typ) ICC Supply Current20µA Standby Supply Current<1µA Shutdown (MAX1897) Supply CurrentSmall 16-Pin QSOP (MAX1887), Compact 20-Pin 5mm x 5mm QFN (MAX1897), or 20-Pin 5mm x 5mm Thin QFN (MAX1897)
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V+ to GND .............................................................-0.3V to +30V
VCC, VDD to GND (Note 3) ......................................-0.3V to +6V
PGND to GND.....................................................................±0.3V
TRIG, LIMIT to GND .................................................-0.3V to +6V
SHDN to GND (MAX1897).........................................-0.3V to +6V
ILIM, CM+, CM-, CS+, CS-, COMP
to GND........................................................-0.3V to (VCC + 0.3V)
TON, POL to GND (MAX1897) ......................-0.3V to (VCC + 0.3V)
DL to PGND..................................................-0.3V to (VDD + 0.3V)
BST to GND..............................................................-0.3V to +36V
DH to LX.....................................................-0.3V to (VBST + 0.3V)
LX to BST..................................................................-6V to +0.3V
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW
20-Pin 5mm x 5mm QFN (derate 20.0mW/°C
above +70°C)................................................................1.60W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Post a Buying Lead
Required Field 
