19-2188; Rev 1; 9/02
Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
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) ICC 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
PIN-PACKAGE
MAX1887EEE
-40°C to +85°C
16 QSOP
MAX1897EGP*
-40°C to +85°C
20 QFN 5mm ✕ 5mm
MAX1897ETP
-40°C to +85°C
20 Thin QFN 5mm ✕ 5mm
*Contact factory for availability.
V+
BST
Applications
LIMIT
20
TOP VIEW
ILIM
Pin Configuration
TRIG
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.
Features
o Quick-PWM Slave Controller
19
18
17
16
Notebook Computers
CM+
1
15
LX
CPU Core Supply
CM-
2
14
DH
Single-Stage (BATT to VCORE) Converters
TON
3
13
SHDN
Two-Stage (5V to VCORE) Converters
CS-
4
12
VCC
CS+
5
11
VDD
Servers/Desktop Computers
MAX1897
6
Quick-PWM is a registered trademark of Maxim Integrated
Products, Inc.
8
9
10
POL
GND
PGND
DL
Typical Operating Circuit appears at end of data sheet.
7
COMP
Telecom
THIN QFN 5mm x 5mm
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1887/MAX1897
General Description
The MAX1887/MAX1897 step-down slave controllers are
intended for low-voltage, high-current, multiphase DC-toDC 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.
