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MAX5974B

产品描述SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, QCC16
产品类别电源/电源管理   
文件大小1MB,共28页
制造商Maxim(美信半导体)
官网地址https://www.maximintegrated.com/en.html
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MAX5974B概述

SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, QCC16

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MAX5974A/MAX5974B/
MAX5974C/MAX5974D
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
General Description
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.
Features
Peak Current-Mode Control, Active-Clamped Forward
PWM Controller
Regulation Without Optocoupler (MAX5974A/
MAX5974B)
Internal 1% Error Amplifier
100kHz to 600kHz Programmable ±8% 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
Internal 18V Zener Clamp on Supply Input
3mm x 3mm, Lead-Free, 16-Pin TQFN-EP
Applications
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
PoE IEEE
®
802.3af/at Powered Devices
High-Power PD (Beyond the 802.3af/at Standard)
Active-Clamped Forward DC-DC Converters
IP Phones
Wireless Access Nodes
Security Cameras
Ordering Information/Selector Guide
appears at end of data
sheet.
19-5331; Rev 7; 12/17
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