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PDF MAX5015 Data sheet ( Hoja de datos )
| Número de pieza | MAX5015 | |
| Descripción | Current-Mode PWM Controllers | |
| Fabricantes | Maxim Integrated | |
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19-2082; Rev 0; 7/01
EVAALVUAAILTAIOBNLEKIT
Current-Mode PWM Controllers with Integrated
Startup Circuit for Isolated Power Supplies
General Description
The MAX5014/MAX5015 integrate all the building
blocks necessary for implementing DC-DC fixed-fre-
quency isolated power supplies. These devices are
current-mode controllers with an integrated high-volt-
age startup circuit suitable for isolated telecom/industri-
al voltage range power supplies. Current-mode control
with leading-edge blanking simplifies control-loop
design and internal ramp compensation circuitry stabi-
lizes the current loop when operating at duty cycles
above 50% (MAX5014). The MAX5014 allows 85%
operating duty cycle and could be used to implement
flyback converters, whereas the MAX5015 limits the
operating duty cycle to less than 50% and can be used
in single-ended forward converters. A high-voltage
startup circuit allows these devices to draw power
directly from the 18V to 110V input supply during start-
up. The switching frequency is internally trimmed to
275kHz ±10%, thus reducing magnetics and filter com-
ponent costs.
The MAX5014/MAX5015 are available in 8-pin SO
packages. An evaluation kit (MAX5015EVKIT) is also
available.
Warning: The MAX5014/MAX5015 are designed to
operate with high voltages. Exercise caution.
Applications
Telecom Power Supplies
Industrial Power Supplies
Networking Power Supplies
Isolated Power Supplies
TOP VIEW
Pin Configuration
Features
o Wide Input Range: (18V to 110V) or (13V to 36V)
o Current-Mode Control
o Leading-Edge Blanking
o Internally Trimmed 275kHz ±10% Oscillator
o Low External Component Count
o Soft-Start
o High-Voltage Startup Circuit
o Pulse-by-Pulse Current Limiting
o Thermal Shutdown
o SO-8 Package
Ordering Information
PART
TEMP. RANGE
MAX5014CSA*
0°C to +70°C
MAX5014ESA*
-40°C to +85°C
MAX5015CSA*
0°C to +70°C
MAX5015ESA*
-40°C to +85°C
*See Selector Guide at end of data sheet.
PIN-PACKAGE
8-SO
8-SO
8-SO
8-SO
Typical Operating Circuit
VIN
VDD
V+
NDRV
MAX5015
CS
SS_SHDN
GND
VCC
VOUT
V+ 1
VDD 2
OPTO 3
SS_SHDN 4
MAX5014/
MAX5015
8 VCC
7 NDRV
6 GND
5 CS
OPTO
OPTOCOUPLER
8-SO
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Current-Mode PWM Controllers with Integrated
Startup Circuit for Isolated Power Supplies
Typical Operating Characteristics (continued)
(V+ = 48V, VDD = 13V, NRDV is open circuit, TA = +25°C, unless otherwise noted.)
271.0
270.5
270.0
269.5
269.0
268.5
268.0
267.5
267.0
0
NDRV FREQUENCY vs. VDD
VOPTO = 4V, CS = GND
5 10 15 20 25 30 35 40
VDD (V)
MAX5015 MAXIMUM DUTY
CYCLE vs. VDD
48.0
47.9
47.8 VOPTO = 4V, CS = GND
47.7
47.6
47.5 DRIVER POWERED
47.4 FROM VDD
47.3
47.2 DRIVER POWERED
47.1 FROM V+
47.0
0
5 10 15 20 25 30 35
VDD (V)
40
VCC vs. VDD
10.2
10.1
DEVICE POWERED FROM VDD
10.0
9.9
9.8
9.7
9.6
9.5
0
DEVICE POWERED
FROM V+
5 10 15 20 25 30 35 40
VDD (V)
1.40
1.39
1.38
1.37
1.36
1.35
1.34
1.33
1.32
1.31
0
V+ SUPPLY CURRENT vs.
V+ VOLTAGE
VOPTO = 4V, CS = GND, VDD = 0
20 40 60 80 100
V+ VOLTAGE (V)
VCC VOLTAGE vs. VCC CURRENT
10.4
V+ = 110V, OPTO = CS = GND
10.2
VDD = 36V
10.0
9.8
VDD = 13V
9.6
9.4
9.2
9.0
0
5.0 10.0 15.0
VCC CURRENT (mA)
20.0
V+ INPUT CURRENT vs. VOLTAGE
(AFTER STARTUP)
12
10
VOPTO = 4V, CS = GND, VDD = 13V
8
6
4
2
0
0 10 20 30 40 50 60 70 80 90 100 110
V+ VOLTAGE (V)
VCC VOLTAGE vs. VCC CURRENT
10.0
9.9 VDD = OPTO = CS = GND
V+ = 110V
9.8 V+ = 90V
9.7
V+ = 72V
V+ = 48V
9.6
9.5 V+ = 36V
9.4 V+ = 24V
9.3
9.2
9.1
9.0
0
5.0 10.0 15.0
VCC CURRENT (mA)
20.0
_______________________________________________________________________________________ 5
5 Page 
Current-Mode PWM Controllers with Integrated
Startup Circuit for Isolated Power Supplies
VREF = R2
VOUT R1 + R2
where VREF is the reference voltage of the shunt
regulator, and R1 and R2 are the resistors shown in
Figures 2 and 3.
3) The turns ratio of the transformer is calculated based
on the minimum input voltage and the lower limit of
the maximum duty cycle for the MAX5015 (44%). To
enable the use of MOSFETs with drain-source
breakdown voltages of less than 200V use the
MAX5015 with the 50% maximum duty cycle.
Calculate the turns ratio according to the following
equation:
( )NS ≥ VOUT + VD1 × DMAX
NP DMAX × VIN_MIN
where:
NS/NP = Turns ratio (NS is the number of secondary
turns and NP is the number of primary turns).
VOUT = Output voltage (5V).
VD1 = Voltage drop across D1 (typically 0.5V for
power Schottky diodes).
DMAX = Minimum value of maximum operating duty
cycle (44%).
VIN_MIN = Minimum Input voltage (36V).
In this example:
NS ≥ 5V +(0.5V × 0.44) = 0.330
NP 0.44 × 36V
Choose NP based on core losses and DC resis-
tance. Use the turns ratio to calculate NS, rounding
up to the nearest integer. In this example NP = 14
and NS = 5.
For a forward converter choose a transformer with a
magnetizing inductance in the neighborhood of
200µH. Energy stored in the magnetizing inductance
of a forward converter is not delivered to the load
and must be returned back to the input; this is
accomplished with the reset winding.
The transformer primary to secondary leakage
inductance should be less than 1µH. Note that all
leakage energy will be dissipated across the MOS-
FET. Snubber circuits may be used to direct some or
all of the leakage energy to be dissipated across a
resistor.
To calculate the minimum duty cycle (DMIN) use the
following equation:
=
DMIN
=
VOUT
VIN_MAX
×
NS
NP
- VD1
= 19.8
where VIN_MAX is the maximum input voltage (72V).
4) The reset winding turns ratio (NR/NP) needs to be
low enough to guarantee that the entire energy in
the transformer is returned to V+ within the off cycle
at the maximum duty cycle. Use the following equa-
tion to determine the reset winding turns ratio:
NR
≤
NP
×
1- DMAX
DMAX ′
′
where:
NR/NP = Reset winding turns ratio.
DMAX’ = Maximum value of Maximum Duty Cycle.
NR
≤ 14
×
1- 0.5
0.5
= 14
Round NR to the nearest smallest integer.
The turns ratio of the reset winding (NR/NP) will
determine the peak voltage across the N-channel
MOSFET.
Use the following equation to determine the maxi-
mum drain-source voltage across the N-channel
MOSFET:
VDSMAX ≥ VIN_MAX × 1 +
NP
NR
VDSMAX = Maximum MOSFET drain-source voltage.
VIN_MAX = Maximum input voltage.
VDSMAX ≥ 72V × 1
+
14
14
= 144V
Choose MOSFETs with appropriate avalanche
power ratings to absorb any leakage energy.
5) Choose the tertiary winding turns ratio (NT/NP) so
that the minimum input voltage provides the mini-
mum operating voltage at VDD (13V). Use the follow-
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MAX5015.PDF ] | |
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