MAX5090ASLASHBSLASHC datasheet(7/17 Pages) MAXIM

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Detailed Description

The MAX5090 step-down DC-DC converter operates from

a 6.5V to 76V input voltage range. A unique voltage-mode

control scheme with voltage feed-forward and an internal

switching DMOS FET provides high efficiency over a wide

input voltage range. This pulse-width-modulated convert-

er operates at a fixed 127kHz switching frequency or can

be synchronized with an external system clock frequency.

The device also features automatic pulse-skipping mode

to provide high efficiency at light loads. Under no load,

the MAX5090 consumes only 310µA, and in shutdown

mode, consumes only 20µA. The MAX5090 also features

undervoltage-lockout, hiccup-mode output short-circuit

protection and thermal shutdown.

ON/OFF/Undervoltage Lockout (UVLO)

Use the ON/OFF function to program the external UVLO

threshold at the input. Connect a resistive voltage-divider

from VIN to SGND with the center node to ON/OFF, as

shown in Figure 1. Calculate the threshold value by using

the following formula:

UVLO(TH)

1.38



+×





Set the external VUVLO(TH) to greater than 6.45V. The

maximum recommended value for R2 is less than 1MΩ.

ON/OFF is a logic input and can be safely driven to the full

VIN range. Connect ON/OFF to VIN for automatic startup.

Drive ON/OFF to ground to shut down the MAX5090.

Shutdown forces the internal power MOSFET off, turns off

all internal circuitry, and reduces the VIN supply current to

20µA (typ). The ON/OFF rising threshold is 1.546V (max).

Before any operation begins, the voltage at ON/OFF must

exceed 1.546V. The ON/OFF input has 100mV hysteresis.

If the external UVLO threshold-setting divider is not used,

an internal undervoltage-lockout feature monitors the

supply voltage at VIN and allows the operation to start

when VIN rises above 6.45V (max). The internal UVLO

rising threshold is set at 6.17V with 0.5V hysteresis.

The VIN and VON/OFF voltages must be above 6.5V and

1.546V, respectively, for proper operation.

NAME

FUNCTION

1, 2

Source Connection of Internal High-Side Switch

BST

Boost Capacitor Connection. Connect a 0.22µF ceramic capacitor from BST to LX.

VIN

Input Voltage. Bypass VIN to SGND with a low-ESR capacitor as close as possible to the device.

Internal Regulator Output. Bypass VD to PGND with a 3.3µF/10V or greater ceramic capacitor.

SYNC

Synchronization Input. Connect SYNC to an external clock for synchronization. Connect to SGND to

select the internal 127kHz switching frequency.

Soft-Start Capacitor Connection. Connect an external capacitor from SS to SGND to adjust the

soft-start time.

Output Sense Feedback Connection.

For fixed output voltage (MAX5090A/MAX5090B), connect FB to VOUT.

For adjustable output voltage (MAX5090C), use an external resistive voltage-divider to set VOUT.

VFB regulating set point is 1.228V.

ON/OFF

Shutdown Control Input. Pull ON/OFF low to put the device in shutdown mode. Drive ON/OFF high for

normal operation. Connect ON/OFF to VIN with short leads for always-on operation.

SGND

Signal Ground. SGND must be connected to PGND for proper operation.

11, 15, 16

N.C.

No Connection. Not internally connected.

PGND

Power Ground

13, 14

DRAIN

Internal High-Side Switch Drain Connection

—

Exposed Pad. Solder EP to SGND plane to aid in heat dissipation. Do not use as the only electrical

ground connection.

MAX5090A/B/C

2A, 76V, High-Efficiency MAXPower

Step-Down DC-DC Converters

www.maximintegrated.com

Maxim Integrated │ 7

Pin Description

MAX5090A/B/C Datasheet(PDF) 7 Page - Maxim Integrated Products

MAX5090A/B/C Datasheet(HTML) 7 Page - Maxim Integrated Products

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