MAX1887 Datasheet, PDF (1/33 Pages) Maxim Integrated Products – Quick-PWM Slave Controllers for Multiphase, Step-Down

19-2188; Rev 1; 9/02
Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
General Description
The MAX1887/MAX1897 step-down slave controllers are
intended for low-voltage, high-current, multiphase DC-to-
DC applications. The MAX1887/MAX1897 slave con-
trollers 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 tran-
sient 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 cir-
cuitry.
The MAX1887/MAX1897 provide the same high effi-
ciency, 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 cur-
rent-sense resistors. These differential inputs and the
adjustable current-limit threshold derived from an exter-
nal reference allow the slave controller to accurately
balance the inductor currents and provide precise cur-
rent-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 mas-
ter’s low-side gate driver, which staggers the on-times
of both master and slave, providing out-of-phase oper-
ation that can reduce the input ripple current and con-
sequently the number of input capacitors. The
MAX1897 features a selectable trigger polarity, allowing
out-of-phase or simultaneous in-phase operation.
Applications
Notebook Computers
CPU Core Supply
Single-Stage (BATT to V_CORE) Converters
Two-Stage (5V to V_CORE) Converters
Servers/Desktop Computers
Telecom
Typical Operating Circuit appears at end of data sheet.
Quick-PWM is a registered trademark of Maxim Integrated
Products, Inc.
Features
o Quick-PWM Slave Controller
o Precise, Active Current Balance (±1.25mV )
o Accurate, Adjustable Current-Limit Threshold
o Optimized for Low-Output Voltages (≤2V)
o 4V to 28V Battery Input Range
o Fixed 300kHz (MAX1887) or Selectable
200kHz/300kHz/550kHz (MAX1897) Switching
Frequency
o Drive Large Synchronous-Rectifier MOSFETs
o 525µA (typ) I_CC Supply Current
o 20µA Standby Supply Current
o <1µA Shutdown (MAX1897) Supply Current
o Small 16-Pin QSOP (MAX1887), Compact
20-Pin 5mm x 5mm QFN (MAX1897), or
20-Pin 5mm x 5mm Thin QFN (MAX1897)
Ordering Information
PART
TEMP RANGE
MAX1887EEE -40°C to +85°C
MAX1897EGP* -40°C to +85°C
MAX1897ETP -40°C to +85°C
*Contact factory for availability.
PIN-PACKAGE
16 QSOP
20 QFN 5mm ✕ 5mm
20 Thin QFN 5mm ✕ 5mm
Pin Configuration
TOP VIEW
20 19 18 17 16
CM+ 1
CM- 2
TON ₃
CS- 4
CS+ 5
MAX1897
15 LX
14 DH
13 ^SHDN
12 V_CC
11 VDD
6 7 8 9 10
THIN QFN 5mm x 5mm
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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