MAX1858A Datasheet, PDF (1/22 Pages) Maxim Integrated Products – Dual 180° Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR

19-2966; Rev 0; 10/03
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Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
General Description
The MAX1858A/MAX1875A/MAX1876A dual, synchro-
nized, step-down controllers generate two outputs from
input supplies ranging from 4.5V 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 by another MAX1858A/MAX1875A/MAX1876A or a
system clock. One MAX1858A/MAX1875A/MAX1876A
can be set to generate an in-phase, or 90° out-of-
phase, clock signal for synchronization with additional
controllers. This allows two controllers to operate either
as an interleaved two- or four-phase system with each
output shifted by 90°. The MAX1858A/MAX1875A/
MAX1876A feature soft-start. The MAX1858A also fea-
tures first-on/last-off power sequencing and soft-stop.
The MAX1858A/MAX1875A/MAX1876A eliminate 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 dur-
ing output-overload conditions or output short-circuit
faults without requiring a current-sense resistor.
Adjustable foldback current limit reduces power dissipa-
tion during short-circuit conditions. The MAX1858A/
MAX1876A include a power-on reset (POR) output to sig-
nal the system when both outputs reach regulation.
The MAX1858A/MAX1875A/MAX1876A ensure that the
output voltage does not swing negative when the input
power is removed or when EN is driven low. The
MAX1875A/MAX1876A also allow prebias startup with-
out discharging the output.
The MAX1858A/MAX1875A/MAX1876A are available in a
24-pin QSOP package. Use the MAX1875 evaluation kit
or the MAX1858 evaluation kit to evaluate the
MAX1858A/MAX1875A/MAX1876A.
Applications
Network Power Supplies
Telecom Power Supplies
DSP, ASIC, and FPGA Power Supplies
Set-Top Boxes
Broadband Routers
Servers
Desknote Computers
Features
o 4.5V to 23V Input Supply Range
o 0 to 18V Output Voltage Range (Up to 10A)
o Adjustable Lossless Foldback Current Limit
o Adjustable 100kHz to 600kHz Switching
Frequency
o Optional Synchronization
o Clock Output for Master/Slave Synchronization
o 4 x 90° Out-of-Phase Step-Down Converters
(Using Two Controllers, Figure 7)
o Prebias Startup (MAX1875A/MAX1876A)
o Power Sequencing (MAX1858A)
o RST Output with 140ms Minimum Delay
(MAX1858A/MAX1876A)
o Fixed-Frequency Pulse-Width Modulation (PWM)
Operation
Ordering Information
PART
MAX1858AEEG
MAX1875AEEG
MAX1876AEEG
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 QSOP
24 QSOP
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
MAX1858A
MAX1875A
MAX1876A
QSOP
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 (N.C.)
() ARE FOR THE MAX1875A ONLY
________________________________________________________________ Maxim Integrated Products 1
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