MAX726CCK ,5A/2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsELECTRICAL CHARACTERISTICS(V = 25V, T = T to T , unless otherwise noted.)IN j MIN MAXPARAMETER COND ..
MAX726ECK ,5A/2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsMAX724/MAX72619-0107; Rev 3; 9/955A/2A Step-Down, PWM,Switch-Mode DC-DC Regulators_______________
MAX727CCK ,5V/3.3V/3V 2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsELECTRICAL CHARACTERISTICS (continued)(V = 25V, T = T to T , unless otherwise noted.)IN j MIN MAXPA ..
MAX727ECK ,5V/3.3V/3V 2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsApplicationsMAX728ECK -40°C to +85°C 5 TO-220Multiple-Output Buck ConverterMAX729CCK 0°C to +70°C 5 ..
MAX727ECK ,5V/3.3V/3V 2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsELECTRICAL CHARACTERISTICS(V = 25V, T = T to T , unless otherwise noted.)IN j MIN MAXPARAMETER COND ..
MAX728ECK ,5V/3.3V/3V 2A Step-Down / PWM / Switch-Mode DC-DC RegulatorsFeatures' Input Range: Up to 40VThe MAX727/MAX728/MAX729 are monolithic, bipolar,pulse-width modula ..
MB4M ,MINIATURE GLASS PASSIVATED SINGLE-PHASE BRIDGE RECTIFIERapplications0.205 (5.21)0.179 (4.55)0.195 (4.95)Mechanical Data0.049 (1.24)0.039 (0.99)0.106 (2.70) ..
MB4S ,Bridge RectifiersThermal Characteristics (T = 25°C unless otherwise noted)AParameter Symbol MB2S MB4S MB6S UnitDevic ..
MB4S_NL ,0.5A Bridge RectifierFeatures• Low leakage+ +- +• Surge overload rating:35 amperes peak.~ ~• Ideal for printed cir ..
MB501 , TECHNICAL SPECIFICATIONS OF SINGLE-PHASE SILICON BRIDGE RECTIFIER
MB501 , TECHNICAL SPECIFICATIONS OF SINGLE-PHASE SILICON BRIDGE RECTIFIER
MB501L ,TWO MODULE PRESCALERSA ust 1995 I do
'l'fi1'j,','ltf, f FUJITSU
M350 f L/504/504L
TWO MODUL US PRESCALERS
TWO MO ..
MAX724CCK-MAX724CCK+-MAX724ECK+-MAX726CCK-MAX726ECK
5A/2A Step-Down / PWM / Switch-Mode DC-DC Regulators
_______________General DescriptionThe MAX724/MAX726 are monolithic, bipolar, pulse-
width modulation (PWM), switch-mode DC-DC regula-
tors optimized for step-down applications. The
MAX724 is rated at 5A, and the MAX726 at 2A. Few
external components are needed for standard opera-
tion because the power switch, oscillator, and control
circuitry are all on-chip. Employing a classic buck
topology, these regulators perform high-current step-
down functions, but can also be configured as invert-
ers, negative boost converters, or flyback converters.
These regulators have excellent dynamic and transient
response characteristics, while featuring cycle-by-cycle
current limiting to protect against overcurrent faults and
short-circuit output faults. The MAX724/MAX726 also
have a wide 8V to 40V input range in the buck step-
down configuration. In inverting and boost configura-
tions, the input can be as low as 5V.
The MAX724/MAX726 are available in a 5-pin TO-220
package. The devices have a preset 100kHz oscillator
frequency and a preset current limit of 6.5A(MAX724)
or 2.6A (MAX726).
_______________________ApplicationsDistributed Power from High-Voltage Buses
High-Current, High-Voltage Step-Down Applications
High-Current Inverter
Negative Boost Converter
Multiple-Output Buck Converter
Isolated DC-DC Conversion
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DCRegulators
________________________________________________________________Maxim Integrated Products1
__________________Pin Configuration
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.19-0107; Rev 3; 9/95
___________________________FeaturesInput Range:Up to 40V5A On-Chip Power Switch (MAX724)
2A On-Chip Power Switch (MAX726)Adjustable Output:2.5V to 35V100kHz Switching FrequencyExcellent Dynamic CharacteristicsFew External Components8.5mAQuiescent CurrentTO-220 Package
______________Ordering Information
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators_______________________________________________________________________________________Input Voltage..................................................45V
Switch Voltage with Respect to Input Voltage................50V
Switch Voltage with Respect to Ground Pin (VSWNegative)
(Note 1).....................................................35V
Feedback Pin Voltage................................-0.3V, +10V
Operating Temperature Ranges
MAX72_CCK.....................................0°C to +70°C
MAX72_ECK....................................-40°C to +85°C
Junction Temperature Ranges
MAX72_CCK....................................0°C to +125°C
MAX72_ECK..................................-40°C to +125°C
Storage Temperature Range...................-65°C to +160°C
Lead Temperature (soldering, 10sec)....................+300°C
ELECTRICAL CHARACTERISTICS(VIN= 25V, Tj= TMINto TMAX, unless otherwise noted.)
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.
ABSOLUTE MAXIMUM RATINGS
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators
_______________________________________________________________________________________3
ELECTRICAL CHARACTERISTICS (continued)(VIN= 25V, Tj= TMINto TMAX, unless otherwise noted.)
Note 1:Do not exceed switch-to-input voltage limitation.
Note 2:For switch currents between 1A and 5A (2A for MAX726), maximum switch-on voltage can be calculated via linear
interpolation.
Note 3:By setting the feedback pin (FB) to 2.5V, the VCpin is forced to its low clamp level and the switch duty cycle is forced to
zero, approximating the zero load condition.
Note 4:For proper regulation, total voltage from VINto GND must be ‡8V after start-up.
Note 5:To avoid extremely short switch-on times, the switch frequency is internally scaled down when VFBis less than 1.3V. Switch-
current limit is tested with VFBadjusted to give a 1µs minimum switch-on time.
Note 6:Guaranteed, not production tested.
__________________________________________Typical Operating CharacteristicsMAX724
STEP-DOWN CONVERTER EFFICIENCY
vs. OUTPUT CURRENT
OUTPUT CURRENT (A)
EFFICIENCY (%)5
SUPPLY CURRENT
vs. JUNCTION TEMPERATURE
JUNCTION TEMPERATURE (°C)
SUPPLY CURRENT (mA)
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE
VIN INPUT VOLTAGE (V)
QUIESCENT SUPPLY CURRENT (mA)30
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators_______________________________________________________________________________________REFERENCE VOLTAGE
vs. JUNCTION TEMPERATURE
JUNCTION TEMPERATURE (°C)
REFERENCE VOLTAGE (V)
SWITCH-ON VOLTAGE
vs. SWITCH CURRENT
SWITCH CURRENT (A)
SWITCH-ON VOLTAGE (V)
SWITCHING FREQUENCY
vs. JUNCTION TEMPERATURE
JUNCTION TEMPERATURE (°C)
SWITCHING FREQUENCY (kHz)
ERROR-AMPLIFIER PHASE AND gM
FREQUENCY (Hz)
TRANSCONDUCTANCE (
mho)
10M
10k1M
100k
PHASE (degrees)
SWITCHING FREQUENCY
vs. FEEDBACK PIN VOLTAGE
FB VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
FEEDBACK PIN CURRENT
vs. FB VOLTAGE
FB VOLTAGE (V)
FB CURRENT (
OUTPUT CURRENT LIMIT
vs. TEMPERATURE
JUNCTION TEMPERATURE (°C)
OUTPUT CURRENT LIMIT (A)
____________________________Typical Operating Characteristics (continued)
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators
_______________________________________________________________________________________5
______________________________________________________________Pin Description
_________________Detailed DescriptionThe MAX724/MAX726 are complete, single-chip, pulse-
width modulation (PWM), step-down DC-DCconverters
(Figure 1). All oscillator (100kHz), control, and current-
limit circuitry, including a 5A power switch (2A for
MAX726), are included on-chip. The oscillator turns on
the switch (VSW) at the beginning of each clock cycle.
The switch turns off at a point later in the clock cycle,
which is a function of the signal provided by the error
amplifier. The maximum switch duty cycle is approxi-
mately 93% at the MAX724/MAX726's 100kHz switch-
ing frequency.
Both the input (FB) and output (VC) of the error
amplifier are brought out to simplify compensation.
Most applications require only a single series RC
network connected from VCto ground. The error
amplifier is a transconductance amplifier with a gMof
approximately 5000mmho. When slewing, VCcan
source about 140mA, and sink about 1.1mA. This
asymmetry helps minimize start-up overshoot by
allowing the amplifier output to slew more quickly in
the negative direction.
Current limiting is provided by the current-limit com-
parator. If the current-limit threshold is exceeded, the
switch cycle terminates within about 600ns. The cur-
rent-limit threshold is internally set to approximately
6.5A (2.6A for MAX726). VSWis a power NPN, internally
driven by the PWM controller circuitry. VSWcan swing
35V below ground and is rated for 5A (2A for MAX726).
Basic Step-Down ApplicationFigure 2 shows the MAX724/MAX726 in a basic step-
down DC-DC converter. Typical MAX724 waveforms
are shown in Figure 3 for VIN= 20V, VOUT= 5V, L =
50mH, and IOUT= 3A and 0.16A. Two sets of wave-
forms are shown. One set shows high load current (3A)
where inductor current never falls to zero during the
switch "off-cycle" (continuous-conduction mode, CCM).
The second set of waveforms, at low output current
(0.16A), shows inductor current at zero during the latter
half of the switch off-cycle (discontinuous-conduction
mode, DCM). The transition from CCM to DCM occurs
at an output current (IDCM) that can be derived with the
following equation:
IDCM=(VOUT+ VD) [(VIN- VSW) - (VOUT+VD)]
2 (VIN- VSW) fOSCL
where VDis the diode forward voltage drop, VSWis the
voltage drop across the switch, and fOSC= 100kHz. In
most applications, the distinction between CCM and
DCM is academic since actual performance differences
are minimal. All CCM designs can be expected to exhibit
DCM behavior at some level of reduced load current.
MAX724/MAX726
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators_______________________________________________________________________________________In DCM, ringing occurs at VSWin the latter part of the
switch off-cycle. This is due to the inductor resonating
with the parallel capacitance of the catch diode and the
VSWnode. This ringing is harmless and does not
appear at the output. Furthermore, attempts to damp
this ringing by adding circuitry will reduce efficiency
and are not advised. No off-state ringing occurs in
CCM because the diode always conducts during the
switch-off time and consequently damps any reso-
nance at VSW.
_______________Component SelectionTable 1 lists component suppliers for inductors, capaci-
tors, and diodes appropriate for use with the
MAX724/MAX726. Be sure to observe specified ratings
for all components.
Table 1. Component Suppliers
Surface-Mount Components(for designs typically below 2A)Inductors:Sumida Electric - CDR125 Series
USA:Phone (708) 956-0666
Japan:Phone 81-3607-5111
FAX 81-3607-5144
Coiltronics - CTXseries
USA:Phone (305) 781-8900
FAX (305) 782-4163
Capacitors:Matsuo - 267 series
USA:Phone (714) 969-2491
FAX (714) 960-6492
Japan:Phone 81-6337-6450
Sprague - 595D series
USA:Phone (603) 224-1961
FAX (603) 224-1430
Diodes:Motorola - MBRS series
USA:Phone (602) 244-5303
FAX (602) 244-4015
Nihon - NSQ series
USA:Phone (805) 867-2555
FAX (805) 867-2556
Japan:Phone 81-3-3494-7411
FAX 81-3-3494-7414
Through-Hole ComponentsInductors:Sumida - RCH-110 series
(see above for phone number)
Cadell-Burns - 7070, 7300, 6860, and 7200 series
USA:Phone (516) 746-2310
FAX (516) 742-2416
Renco - various series
USA:Phone (516) 586-5566
FAX (516) 586-5562
Coiltronics - various series
(see above for phone number)
Capacitors:Nichicon - PLseries low-ESR electrolytics
USA:Phone (708) 843-7500
FAX (708) 843-2798
Japan:Phone 81-7-5231-8461
FAX 81-7-5256-4158
United Chemi-Con - LXFseries
USA:Phone (714) 255-9500
FAX (714) 255-9400
Sanyo - OS-CON low-ESRorganic semiconductor
USA:Phone (619) 661-6835
FAX (619) 661-1055
Japan:Phone 81-7-2070-6306
FAX 81-7-2070-1174
Diodes:General Purpose - 1N5820-1N5825
Motorola - MBRand MBRD series
(see above for phone number)
