MAX1856EUB+ Maxim Integrated Products, MAX1856EUB+ Datasheet

MAX1856EUB+

Manufacturer Part Number

MAX1856EUB+

Description

IC PS PWM SLIC SYNCH 10-UMAX

Manufacturer

Maxim Integrated Products

Datasheet

1.MAX1856EUB.pdf (18 pages)

Specifications of MAX1856EUB+

Pwm Type

Current Mode

Number Of Outputs

Frequency - Max

575kHz

Duty Cycle

94%

Voltage - Supply

3 V ~ 28 V

Buck

Boost

Flyback

Yes

Inverting

Yes

Doubler

Divider

Cuk

Isolated

Operating Temperature

0°C ~ 85°C

Package / Case

10-MSOP, Micro10™, 10-uMAX, 10-uSOP

Frequency-max

575kHz

Output Voltage

0 V to - 185 V

Output Current

0.3 A

Input Voltage

3 V to 28 V

Switching Frequency

500 KHz

Mounting Style

SMD/SMT

Duty Cycle (max)

94 %

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

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The MAX1856 offers a low-cost solution for generating a

SLIC (ringer and off-hook) power supply. Using standard

off-the-shelf transformers from multiple vendors, the

MAX1856 generates various output voltages: -24V and

-72V (dual output) for both ringer and off-hook supplies for

voice-enabled broadband consumer premises equipment

(CPE), -48V for IP phones and routers, -5V and -15V (sin-

gle or dual output) for DSL CO line drivers, or negative

voltages as high as -185V for MEMS bias supplies. The

output voltages are adjusted with an external voltage

divider.

Due to its wide operating voltage range, the MAX1856

operates from a low-cost, unregulated DC power supply

for cost-sensitive applications like xDSL, cable modems,

set-top boxes, LMDS, MMDS, WLL, and FTTH CPE. The

MAX1856 provides low audio-band noise for talk battery

and a sturdy output capable of handling the ring trip con-

ditions for ring battery.

The operating frequency can be set between 100kHz and

500kHz with an external resistor in free-running mode. For

noise-sensitive applications, the MAX1856’s operating fre-

quency can be synchronized to an external clock over its

operating frequency range.

The flyback topology allows operation close to 50% duty

cycle, offering high transformer utilization, low ripple cur-

rent, and less stress on input and output capacitors.

Internal soft-start minimizes startup stress on the input

capacitor, without any external components.

The MAX1856’s current-mode control scheme does not

require external loop compensation. The low-side current-

sense resistor provides accurate current-mode control

and overcurrent protection.

19-1898; Rev 0; 2/01

Idle Mode is a trademark of Maxim Integrated Products.

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

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

VoIP Ringer and Off-Hook Voltage Generators

Cable and DSL Modems

Set-Top Boxes

Wireless Local Loop

FTTH

LMDS/MMDS

Routers

Industrial Power Supplies

CO DSL Line Driver Supplies

MEMS Bias Supplies

________________________________________________________________ Maxim Integrated Products

General Description

Wide Input Range, Synchronizable,

Applications

PWM SLIC Power Supply

o Low-Cost, Off-the-Shelf Transformer

o 3V to 28V Input Range

o Low Audio-Band Noise on Talk Battery

o Effectively Handles Ring Trip Transients

o Powers 2-, 4-, or 12-Line Equipment

o High Efficiency Extends Battery Life During

o Adjustable 100kHz to 500kHz Switching

o Clock Synchronization

o Internal Soft-Start

o Current-Mode PWM and Idle Mode™ Control

o Logic-Level Shutdown

o 10-Pin µMAX Package

INPUT

3V TO 28V

Life-Line Support Conditions

Frequency

Scheme

MAX1856EUB

PART

LDO

SYNC/SHDN

FREQ

GND

PGND

Typical Operating Circuit

MAX1856

TEMP. RANGE

-40°C to +85°C

Ordering Information

EXT

REF

10 µMAX

PIN-PACKAGE

Features

OUT2

OUT1

-72V

-24V

Related parts for MAX1856EUB+

MAX1856EUB+ Summary of contents

Page 1

... Routers Industrial Power Supplies CO DSL Line Driver Supplies MEMS Bias Supplies Idle Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. PWM SLIC Power Supply ...

Page 2

Wide Input Range, Synchronizable, PWM SLIC Power Supply ABSOLUTE MAXIMUM RATINGS V , SYNC/SHDN to GND .....................................-0.3V to +30V CC PGND to GND .......................................................-0.3V to +0.3V LDO, FREQ, FB GND.....................................-0.3V to +6V EXT, REF to GND......................................-0. ...

Page 3

Wide Input Range, Synchronizable, ELECTRICAL CHARACTERISTICS (continued SYNC/SHDN 5V 5V LDO PARAMETER SYMBOL Minimum EXT Pulse Width Minimum SYNC Input Signal Duty Cycle Minimum SYNC Input Low Pulse Width Maximum SYNC ...

Page 4

Wide Input Range, Synchronizable, PWM SLIC Power Supply ELECTRICAL CHARACTERISTICS (continued SYNC/SHDN 5V 5V LDO PARAMETER SYMBOL Maximum Duty Cycle D Minimum SYNC Input Signal Duty Cycle Minimum SYNC Input Low ...

Page 5

Wide Input Range, Synchronizable, (Circuit of Figure SYNC/SHDN -72V OUTPUT VOLTAGE vs. LOAD CURRENT - 12V 24V IN - -24V OUT1 V ...

Page 6

Wide Input Range, Synchronizable, PWM SLIC Power Supply (Circuit of Figure 12V SYNC/SHDN SUPPLY CURRENT vs. TEMPERATURE 350 310 R = 100kΩ OSC R = 200kΩ 270 OSC 230 R = 500kΩ OSC ...

Page 7

Figure SYNC/SHDN EXITING SHUTDOWN MAX1856 toc21 -20V -40V -60V 4ms/div 5V, 5V/div SYNC SHDN 2A/div ...

Page 8

Wide Input Range, Synchronizable, PWM SLIC Power Supply PIN NAME 5V Linear Regulator Output. The regulator powers all of the internal circuitry, including the EXT gate 1 LDO driver. Bypass LDO to GND with a 1µF or greater ceramic capacitor. ...

Page 9

Wide Input Range, Synchronizable, *INPUT 4.5V TO 24V R5 10Ω 1µ LDO 1µ OSC 200kΩ *INPUT RANGE LIMITED BY OUTPUT POWER REQUIREMENTS. SEE MAXIMUM OUTPUT POWER AND TYPICAL OPERATING CHARACTERISTICS. Figure ...

Page 10

Wide Input Range, Synchronizable, PWM SLIC Power Supply 276kΩ 4 REF 5 FB SLOPE COMP GND 100mV 15mV Figure 2. Functional Diagram cuit (Figure 1) converting a +12V input to a -72V output ...

Page 11

Wide Input Range, Synchronizable, 100kHz to 500kHz frequency, which is set by a resistor (R ) connected from FREQ to GND. The relationship OSC between f and R is: OSC OSC 50 Ω × M kHz = R OSC ƒ ...

Page 12

Wide Input Range, Synchronizable, PWM SLIC Power Supply Table 1. Transformer Selection for Standard Applications INPUT VOLTS (V) OUTPUT VOLTS (V) 5 -48 12 -48 12 -24 and -72 12 -95 and -30 Table 2. Transformer Suppliers VENDOR Coilcraft Coiltronics ...

Page 13

Wide Input Range, Synchronizable, high side and connect a 1000pF capacitor CS between CS and GND. Power MOSFET Selection The MAX1856 drives a wide variety of N-channel power MOSFETs (NFETs). Since the LDO limits the EXT output ...

Page 14

Wide Input Range, Synchronizable, PWM SLIC Power Supply the feedback resistance that cancels the ESR zero. The optimum compensation value is:  1 ESR COUT = C C  FB OUT × 2  ...

Page 15

Wide Input Range, Synchronizable, INPUT 3V TO 28V LDO R OSC Figure 3. Feedback Compensation and Snubber Circuits t ƒ This gives a value of about 22Ω for R7. However, this snubber ...

Page 16

Wide Input Range, Synchronizable, PWM SLIC Power Supply INPUT 4.5V TO 24V R5 10Ω 1µF C LDO 1µF R OSC 200kΩ Figure 4. -48V Output Application Circuit 16 ______________________________________________________________________________________ (2x) 10µF 25V ...

Page 17

Wide Input Range, Synchronizable, Pin Configuration TOP VIEW LDO 1 10 FREQ 2 9 MAX1856 GND 3 8 REF µMAX ______________________________________________________________________________________ PWM SLIC Power Supply TRANSISTOR COUNT: 1538 PROCESS: BiCMOS SYNC/SHDN V CC EXT PGND ...

Page 18

... 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 ____________________ 18 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products ...

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