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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1856 Datasheet

Wide Input Range / Synchronizable / PWM SLIC Power Supply

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MAX1856 pdf
19-1898; Rev 0; 2/01
Wide Input Range, Synchronizable,
PWM SLIC Power Supply
General Description
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.
Applications
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
Idle Mode is a trademark of Maxim Integrated Products.
Features
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
Life-Line Support Conditions
o Adjustable 100kHz to 500kHz Switching
Frequency
o Clock Synchronization
o Internal Soft-Start
o Current-Mode PWM and Idle Mode™ Control
Scheme
o Logic-Level Shutdown
o 10-Pin µMAX Package
PART
MAX1856EUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Typical Operating Circuit
INPUT
3V TO 28V
VCC
SYNC/SHDN
LDO
FREQ
EXT
CS
MAX1856
GND
PGND
FB
REF
1
2
2
2
OUT2
-72V
OUT1
-24V
________________________________________________________________ Maxim Integrated Products 1
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.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1856 Datasheet

Wide Input Range / Synchronizable / PWM SLIC Power Supply

No Preview Available !

MAX1856 pdf
Wide Input Range, Synchronizable,
PWM SLIC Power Supply
ABSOLUTE MAXIMUM RATINGS
VCC, SYNC/SHDN to GND .....................................-0.3V to +30V
PGND to GND .......................................................-0.3V to +0.3V
LDO, FREQ, FB, CS to GND.....................................-0.3V to +6V
EXT, REF to GND......................................-0.3V to (VLDO + 0.3V)
LDO Output Current............................................-1mA to +20mA
LDO Short Circuit to GND ...............................................<100ms
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (TA = +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = SYNC/SHDN, VCC = 5V, VLDO = 5V, ROSC = 200k, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
PWM CONTROLLER
Operating Input Voltage Range
FB Input Current
Load Regulation
Line Regulation
VCC
VCC = VLDO
3 28 V
2.7 5.5 V
IFB VFB = -0.05V
1 50 nA
VCS = 0 to 100mV for 0 to ILOAD(MAX)
0.013
%/mV
Typically 0.0074% per % duty factor on EXT
0.0074
%/%
Current-Limit Threshold
CS Input Current
VCS
ICS CS = GND
85 100 115 mV
1 µA
Idle Mode Current-Sense
Threshold
5 15 25 mV
VCC Supply Current (Note 1)
ICC
Shutdown Supply Current
REFERENCE AND LDO REGULATOR
LDO Output Voltage
VLDO
Undervoltage Lockout
Threshold
VUVLO
VFB = -0.05V, VCC = 3V to 28V
SYNC/SHDN = GND, VCC = 28V
RLDO = 400
5V VCC 28V
3V VCC 28V
VLDO falling edge, 1% hysteresis (typ)
250 400 µA
3.5 6 µA
4.50
2.65
2.40
5.00
2.50
5.50
5.50
2.60
V
V
REF to FB Voltage (Note 2)
REF Load Regulation
VREF
RREF = 10k, CREF = 0.22µF
IREF = 0 to 400µA
1.225
1.250
-2
1.275
-10
V
mV
REF Undervoltage Lockout
Threshold
Rising edge, 1% hysteresis (typ)
1.0 1.1 1.2
V
OSCILLATOR
Oscillator Frequency
Maximum Duty Cycle
fOSC
D
ROSC = 100kΩ ±1%
ROSC = 200kΩ ±1%
ROSC = 500kΩ ±1%
ROSC = 100kΩ ±1%
ROSC = 200kΩ ±1%
ROSC = 500kΩ ±1%
425 500 575
225 250 275 kHz
85 100 115
86 90 94
87 90 93 %
86 90 94
2 _______________________________________________________________________________________


Part Number MAX1856
Description Wide Input Range / Synchronizable / PWM SLIC Power Supply
Maker Maxim
Total Page 18 Pages
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