MAX1858A, MAX1875A, MAX1876A Dual 180° Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR

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The MAX1858A/MAX1875A/MAX1876A dual, synchronized, 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 controller can be synchronized to an external clock generated 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 features 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 during output-overload conditions or output short-circuit faults without requiring a current-sense resistor. Adjustable foldback current limit reduces power dissipation during short-circuit conditions. The MAX1858A/MAX1876A include a power-on reset (POR) output to signal 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 without 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.

Key Features

Applications/Uses

4.5V to 23V Input Supply Range
0 to 18V Output Voltage Range (Up to 10A)
Adjustable Lossless Foldback Current Limit
Adjustable 100kHz to 600kHz Switching Frequency
Optional Synchronization
Clock Output for Master/Slave Synchronization
4 x 90° Out-of-Phase Step-Down Converters (Using Two Controllers, Figure 7)
Prebias Startup (MAX1875A/MAX1876A)
Power Sequencing (MAX1858A)
RST-bar Output with 140ms Minimum Delay (MAX1858A/MAX1876A)
Fixed-Frequency Pulse-Width Modulation (PWM) Operation

	Broadband Routers
	Desknote Computers
	DSP, ASIC, and FPGA Power Supplies
	Network-Power Supplies
	Servers
	Set-Top Boxes
	Telecom Power Supplies

Key Specifications: Switch-Mode DC-DC Power Supplies

Part Number

Topology

V_IN (min) (V)

V_IN (max) (V)

Number of DC-DC Outputs

Digital/VID Programmed Output

Min. Adjustable V_OUT (V)

Max. Adjustable V_OUT (V)

I_OUT (A)

Operating Current, I_CC (max) (mA)

Fixed Freq/PWM Operation

Operating Freq. (kHz)

Internal Power Switch(es)

Synchronous Rectifier

Package

Smallest Available Package (max w/pins) (mm²)

Price^**

MAX1858A

Step-Down

4.5

0.8

Yes

100
600

Yes

QSOP/24

$2.50 @ 1k

MAX1875A

$2.00 @ 1k

MAX1876A

$2.30 @ 1k

See All Switch-Mode DC-DC Power Supplies (421)

Notes:
^**This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.