MAX5974AETE+ Maxim Integrated Products, MAX5974AETE+ Datasheet

Current Mode PWM Controllers ACTIVE-CLAMPED CUR MODE PWM CONTLR

MAX5974AETE+

Manufacturer Part Number
MAX5974AETE+
Description
Current Mode PWM Controllers ACTIVE-CLAMPED CUR MODE PWM CONTLR
Manufacturer
Maxim Integrated Products
Datasheet
1.MAX5974DETE.pdf (26 pages)

Specifications of MAX5974AETE+

Duty Cycle (max)
82 %
Mounting Style
SMD/SMT
Switching Frequency
600 KHz
Operating Supply Voltage
12 V to 21 V
Supply Current
1.8 mA
Maximum Operating Temperature
+ 85 C
Fall Time
14 ns
Minimum Operating Temperature
- 40 C
Rise Time
27 ns
Package / Case
TQFN-16
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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 1; 9/10
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
TOP MARK
General Description
+AHY
+AHZ
+AIA
+AIB
Active-Clamped, Spread-Spectrum,
16 TQFN-EP*
16 TQFN-EP*
16 TQFN-EP*
16 TQFN-EP*
PIN-PACKAGE
Current-Mode PWM Controllers
S Peak Current-Mode Control, Active-Clamped
S Regulation Without Optocoupler (MAX5974A/
S Internal 1% Error Amplifier
S 100kHz to 600kHz Programmable Q8% Switching
S Programmable Frequency Dithering for Low-EMI,
S Programmable Dead Time, PWM Soft-Start,
S Programmable Feed-Forward Maximum Duty-
S Frequency Foldback for High-Efficiency Light-
S Internal Bootstrap UVLO with Large Hysteresis
S 100µA (typ) Startup Supply Current
S Fast Cycle-by-Cycle Peak Current-Limit, 35ns
S 115ns Current-Sense Internal Leading-Edge
S Output Short-Circuit Protection with Hiccup Mode
S Reverse Current Limit to Prevent Transformer
S 3mm x 3mm, Lead-Free, 16-Pin TQFN-EP
UVLO THRESHOLD (V)
Forward PWM Controller
MAX5974B)
Frequency, Synchronization Up to 1.2MHz
Spread-Spectrum Operation
Current Slope Compensation
Cycle Clamp, 80% Maximum Limit
Load Operation
Typical Propagation Delay
Blanking
Saturation Due to Reverse Current
PoE IEEE
High-Power PD (Beyond the 802.3af/at Standard)
Active-Clamped Forward DC-DC Converters
IP Phones
Wireless Access Nodes
Security Cameras
20
10
20
10
®
802.3af/at Powered Devices
Ordering Information
Continuously Connected
Continuously Connected
FEEDBACK MODE
Sample/Hold
Sample/Hold
Applications
Features

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MAX5974AETE+ Summary of contents

Page 1

... 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. PART TOP MARK MAX5974AETE+ +AHY MAX5974BETE+ +AHZ MAX5974CETE+ +AIA MAX5974DETE+ +AIB Note: All devices are specified over the -40° ...

Page 2

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers ABSOLUTE MAXIMUM RATINGS IN to GND ..............................................................-0.3V to +26V EN, NDRV, AUXDRV to GND .....................-0. RT, DT, FFB, COMP, SS, DCLMP, DITHER/SYNC to GND .................................................................-0. GND (MAX5974A/MAX5974B only) ..................-6V ...

Page 3

Active-Clamped, Spread-Spectrum, ELECTRICAL CHARACTERISTICS (continued 12V (for MAX5974A/MAX5974C, bring +2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN unless otherwise noted. Typical values are at T PARAMETER SYMBOL ...

Page 4

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers ELECTRICAL CHARACTERISTICS (continued 12V (for MAX5974A/MAX5974C, bring +2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN unless otherwise noted. Typical values are at ...

Page 5

Active-Clamped, Spread-Spectrum, ELECTRICAL CHARACTERISTICS (continued 12V (for MAX5974A/MAX5974C, bring +2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN unless otherwise noted. Typical values are at T PARAMETER SYMBOL ...

Page 6

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers (V = 12V (for MAX5974A/MAX5974C, bring 2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN IN UVLO WAKE-UP LEVEL vs. TEMPERATURE 20.1 MAX5974A/MAX5974C 20.0 19.9 ...

Page 7

Active-Clamped, Spread-Spectrum 12V (for MAX5974A/MAX5974C, bring 2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN SOFT-START CHARGING CURRENT vs. TEMPERATURE 10.06 10.05 10.04 10.03 10.02 10.01 10.00 9.99 ...

Page 8

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers (V = 12V (for MAX5974A/MAX5974C, bring 2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN DEAD TIME vs. R VALUE DT 400 350 300 250 ...

Page 9

Active-Clamped, Spread-Spectrum 12V (for MAX5974A/MAX5974C, bring 2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN TRANSCONDUCTANCE vs. TEMPERATURE 3.0 2.9 MAX5974C/MAX5974D 2.8 2.7 2.6 2.5 2.4 MAX5974A/MAX5974B 2.3 ...

Page 10

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers (V = 12V (for MAX5974A/MAX5974C, bring 2V, NDRV = AUXDRV = SS = COMP = unconnected, R GND EN V RAMP RESPONSE DCLMP MAX5974A/B/C/D toc35 V DCLMP 2V/div V ...

Page 11

Active-Clamped, Spread-Spectrum, TOP VIEW PIN NAME Dead-Time Programming Resistor Connection. Connect resistor desired dead time between the NDRV and AUXDRV signals. See the Dead Time section to calcu- late the resistor value for a particular dead time. ...

Page 12

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers PIN NAME 6 FB Transconductance Amplifier Inverting Input 7 GND Signal Ground Current Sense with Slope Compensation Input. A resistor connected from CSSC to CS programs the 8 CSSC amount of slope compensation. See the ...

Page 13

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers Block Diagrams 13 ...

Page 14

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers 14 Block Diagrams (continued) ...

Page 15

Active-Clamped, Spread-Spectrum, Detailed Description The MAX5974A/MAX5974B/MAX5974C/MAX5974D are optimized for controlling a 25W to 50W active-clamped, self-driven synchronous rectification forward converter in continuous-conduction mode. The main switch gate driver (NDRV) and the active-clamped switch driver (AUXDRV) are sized to optimize efficiency ...

Page 16

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers EN1 DIGITAL CONTROL R N EN2 Figure 1. Programmable UVLO for the Power Source DIGITAL EN CONTROL N Figure 2. External Control ...

Page 17

Active-Clamped, Spread-Spectrum, startup to provide a slow and smooth increase of the duty cycle to its steady-state value. Calculate the value follows × t SS- where I (10FA typ) is the ...

Page 18

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers Oscillator/Switching Frequency The ICs’ switching frequency is programmable between 100kHz and 600kHz with a resistor R between RT and GND. Use the following formula to determine the appropriate value of R erate the desired output-switching ...

Page 19

Active-Clamped, Spread-Spectrum, Frequency Foldback for High-Efficiency Light-Load Operation The frequency foldback threshold can be programmed from 0 to 20% of the full load current using a resistor from FFB to GND. When V falls below V , the device folds ...

Page 20

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers Typically, f should be set close to 1kHz. The resistor TRI R connected from DITHER/SYNC to RT deter- DITHER mines the amount of dither as follows × %DITHER 3 R DITHER where ...

Page 21

Active-Clamped, Spread-Spectrum, Active Clamp Circuit Traditional clamp circuits prevent transformer saturation by channeling the magnetizing current (I former onto a dissipative RC network. To improve effi- ciency, the active clamp circuit recycles I magnetizing inductance and clamp capacitor ...

Page 22

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers During on-time, the coupled output is − (V × COUPLED- where V is the input supply voltage. S Care must be taken to ensure that the voltage at ...

Page 23

Active-Clamped, Spread-Spectrum 36V TO 57V C BULK 33µ 100kI C IN 1µF 25V R DCLMP1 IN 30. DCLMP2 750 I 1% DCLMP C SS 0.1µF SS MAX5974C R DT MAX5974D 16.9k I ...

Page 24

Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers V S 36V TO 57V C BULK 33µ 63V 100kI R DCLMP1 30. DCLMP2 750 I 1% DCLMP C SS 0.1µF SS MAX5974A R DT MAX5974B 16.9k I ...

Page 25

Active-Clamped, Spread-Spectrum BULK DCLMP1 EN R DCLMP2 DCLMP MAX5974C R MAX5974D DITHER C DITHER DITHER/ SYNC FFB FFB FB COMP R z GND ...

Page 26

... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 26 2010 Maxim Integrated Products © ...

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