MAX1858 Datasheet, PDF (1/21 Pages) Maxim Integrated Products – Dual 180° Out-of-Phase PWM Step-Down Controller with Power Sequencing and POR

19-2432; Rev 0; 7/02
EVALUAATVIOANILKAIBTLMEANUAL
Dual 180° Out-of-Phase PWM Step-Down
Controller with Power Sequencing and POR
General Description
The MAX1858 dual, synchronized, step-down controller
generates two outputs from input supplies ranging from
4.75V to 23V. Each output is adjustable from sub-1V to
18V and supports loads of 10A or higher. Input voltage
ripple and total RMS input ripple current are reduced by
synchronized 180° out-of-phase operation.
The switching frequency is adjustable from 100kHz to
600kHz with an external resistor. Alternatively, the con-
troller can be synchronized to an external clock gener-
ated to another MAX1858 or a system clock. One
MAX1858 can be set to generate an in-phase, or 90°
out-of-phase, clock signal for synchronization with addi-
tional controllers. This allows two controllers to operate
either as an interleaved two- or four-phase system with
each output shifted by 90°. The device also features
“first-on/last-off” power sequencing for compatibility
with DSPs, ASICs, and FPGAs, as well as soft-start and
soft-stop to ensure reliable and repeatable power
sequencing.
The MAX1858 eliminates the need for current-sense
resistors by utilizing the low-side MOSFET’s on-resistance
as a current-sense element. This protects the DC-DC
components from damage during output-overload condi-
tions or when output short-circuit faults without requiring a
current-sense resistor. Adjustable foldback current limit
reduces power dissipation during short-circuit condition.
A power-on reset output signals the system when both
outputs reach regulation.
The MAX1858 is available in a 24-pin QSOP package.
An evaluation kit is available to speed designs.
Applications
Network Power Supplies
Telecom Power Supplies
DSP, ASIC, and FPGA Power Supplies
Set-Top Boxes
Broadband Routers
Servers
Typical Operating Circuit appears at end of data sheet.
Features
o Two Independent Output Voltages
o 180° Out-of-Phase Operation
o 90° Out-of-Phase Operation
(Using Two MAX1858s)
o Foldback Current Limit
o 4.75V to 23V Input Supply Range
o 0 to 18V Output-Voltage Range (Up to 10A)
o >90% Efficiency
o Fixed-Frequency Pulse-Width Modulation (PWM)
Operation
o Adjustable 100kHz to 600kHz Switching
Frequency
o External SYNC Input
o Clock Output for Master/Slave Synchronization
o Power-On/-Off Sequencing with Soft-Start and
Soft-Stop
o RST Output with 140ms Minimum Delay
o Lossless Current Limit (No Sense Resistor)
PART
MAX1858EEG
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
24 QSOP
Pin Configuration
TOP VIEW
COMP2 1
FB2 2
ILIM2 3
OSC 4
V+ 5
REF 6
GND 7
CKO 8
SYNC 9
ILIM1 10
FB1 11
COMP1 12
MAX1858
24 EN
23 DH2
22 LX2
21 BST2
20 DL2
19 V_L
18 PGND
17 DL1
16 BST1
15 LX1
14 DH1
13 RST
QSOP
________________________________________________________________ Maxim Integrated Products 1
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.