max5974 Maxim Integrated Products, Inc., max5974 Datasheet

max5974

Manufacturer Part Number

max5974

Description

Active-clamped, Spread-spectrum, Current-mode Pwm Controllers

Manufacturer

Maxim Integrated Products, Inc.

Datasheet

1.MAX5974.pdf (26 pages)

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Current page: 1 of 26
Download datasheet (3Mb)

The MAX5974_ provide control for wide-input-voltage,

active-clamped, current-mode PWM, forward converters

in Power-over-Ethernet (PoE) powered device (PD) appli-

cations. The MAX5974A/MAX5974C are well-suited for

universal or telecom input range, while the MAX5974B/

MAX5974D also accommodate low input voltage down

to 10.5V.

The devices include several features to enhance supply

efficiency. The AUX driver recycles magnetizing cur-

rent instead of wasting it in a dissipative clamp circuit.

Programmable dead time between the AUX and main

driver allows for zero-voltage switching (ZVS). Under light-

load conditions, the devices reduce the switching fre-

quency (frequency foldback) to reduce switching losses.

The MAX5974A/MAX5974B feature unique circuitry to

achieve output regulation without using an optocoupler,

while the MAX5974C/MAX5974D utilize the traditional

optocoupler feedback method. An internal error amplifier

with a 1% reference is very useful in nonisolated design,

eliminating the need for an external shunt regulator.

The devices feature a unique feed-forward maximum

duty-cycle clamp that makes the maximum clamp volt-

age during transient conditions independent of the line

voltage, allowing the use of a power MOSFET with lower

breakdown voltage. The programmable frequency dither-

ing feature provides low-EMI, spread-spectrum operation.

The MAX5974_ are available in 16-pin TQFN-EP pack-

ages and are rated for operation over the -40°C to +85°C

temperature range.

Note: All devices are specified over the -40°C to +85°C operating temperature range.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc.

19-5331; Rev 0; 6/10

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX5974AETE+

MAX5974BETE+**

MAX5974CETE+

MAX5974DETE+**

PART

________________________________________________________________ _Maxim Integrated Products_ _ 1

**Future product—Contact factory for availability.

TOP_MARK

General Description

+AHY

+AHZ

+AIA

+AIB

Active-Clamped, Spread-Spectrum,

16 TQFN-EP*

PIN-PACKAGE

Current-Mode PWM Controllers

UVLO_THRESHOLD_(V)

Peak_Current-Mode_Control,_Active-Clamped_

Forward_PWM_Controller

Regulation_Without_Optocoupler_(MAX5974A/

MAX5974B)

Internal_1%_Error_Amplifier

100kHz_to_600kHz_Programmable_Q8%_Switching_

Frequency,_Synchronization_Up_to_1.2MHz

Programmable_Frequency_Dithering_for_Low-EMI,_

Spread-Spectrum_Operation

Programmable_Dead_Time,_PWM_Soft-Start,_

Current_Slope_Compensation

Programmable_Feed-Forward_Maximum_Duty-_

Cycle_Clamp,_80%_Maximum_Limit

Frequency_Foldback_for_High-Efficiency_Light-

Load_Operation

Internal_Bootstrap_UVLO_with_Large_Hysteresis

100µA_(typ)_Startup_Supply_Current

Fast_Cycle-by-Cycle_Peak_Current-Limit,_35ns_

Typical_Propagation_Delay

115ns_Current-Sense_Internal_Leading-Edge_

Blanking

Output_Short-Circuit_Protection_with_Hiccup_Mode

Reverse_Current_Limit_to_Prevent_Transformer_

Saturation_Due_to_Reverse_Current

3mm_x_3mm,_Lead-Free,_16-Pin_TQFN-EP

PoE IEEE

High-Power PD (Beyond the 802.3af/at Standard)

Active-Clamped Forward DC-DC Converters

IP Phones

Wireless Access Nodes

Security Cameras

802.3af/at Powered Devices

Ordering Information

Continuously Connected

FEEDBACK_MODE

Sample/Hold

Applications

Features

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