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PDF MAX5003 Data sheet ( Hoja de datos )
| Número de pieza | MAX5003 | |
| Descripción | High-Voltage PWM Power-Supply Controller | |
| Fabricantes | Maxim Integrated | |
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19-1555; Rev 2; 4/02
EVAALVUAAILTAIOBNLEKIT
High-Voltage PWM
Power-Supply Controller
General Description
The MAX5003 high-voltage switching power-supply
controller has all the features and building blocks need-
ed for a cost-effective flyback and forward voltage-
mode control converter. This device can be used to
design both isolated and nonisolated power supplies
with multiple output voltages that operate from a wide
range of voltage sources. It includes a high-voltage
internal start-up circuit that operates from a wide 11V to
110V input range. The MAX5003 drives an external N-
channel power MOSFET and has a current-sense pin
that detects overcurrent conditions and turns off the
power switch when the current-limit threshold is
exceeded. The choice of external power MOSFET and
other external components determines output voltage
and power.
The MAX5003 offers some distinctive advantages: soft-
start, undervoltage lockout, external frequency synchro-
nization, and fast input voltage feed-forward. The
device is designed to operate at up to 300kHz switch-
ing frequency. This allows use of miniature magnetic
components and low-profile capacitors. Undervoltage
lockout, soft-start, switching frequency, maximum duty
cycle, and overcurrent protection limit are all adjustable
using a minimum number of external components. In
systems with multiple controllers, the MAX5003 can be
externally synchronized to operate from a common sys-
tem clock.
Warning: The MAX5003 is designed to operate with
high voltages. Exercise caution.
The MAX5003 is available in 16-pin SO and QSOP pack-
ages. An evaluation kit (MAX5003EVKIT) is also available.
Applications
Telecommunication Power Supplies
ISDN Power Supplies
+42V Automobile Systems
High-Voltage Power-Supply Modules
Industrial Power Supplies
Features
o Wide Input Range: 11V to 110V
o Internal High-Voltage Startup Circuit
o Externally Adjustable Settings
Output Switch Current Limit
Oscillator Frequency
Soft-Start
Undervoltage Lockout
Maximum Duty Cycle
o Low External Component Count
o External Frequency Synchronization
o Primary or Secondary Regulation
o Input Feed-Forward for Fast Line-Transient
Response
o Precision ±2.5% Reference over Rated
Temperature Range
o Thermal Shutdown
Ordering Information
PART
TEMP. RANGE PIN-PACKAGE
MAX5003CEE
0°C to +70°C
16 QSOP
MAX5003CSE
0°C to +70°C
16 Narrow SO
MAX5003C/D
(Note A)
Dice
MAX5003EEE
-40°C to +85°C
16 QSOP
MAX5003ESE
-40°C to +85°C
16 Narrow SO
Note: Dice are designed to operate over a -40°C to +140°C junc-
tion temperature (Tj) range, but are tested and guaranteed at
TA = +25°C.
Pin Configuration
TOP VIEW
V+ 1
INDIV 2
ES 3
FREQ 4
SS 5
REF 6
CON 7
COMP 8
MAX5003
16 VDD
15 VCC
14 NDRV
13 PGND
12 CS
11 AGND
10 MAXTON
9 FB
QSOP/Narrow 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  
High-Voltage PWM
Power-Supply Controller
Typical Operating Characteristics (continued)
(VDD = +12V, RFREQ = 200kΩ, RMAXTON = 200kΩ, TA = +25°C, unless otherwise noted.)
V+ INPUT CURRENT vs. VOLTAGE
3.0
2.5
2.0
1.5
1.0
0.5
VCON = VCOMP = VFB
SWITCHING
0
20 40 60
80
V+ (V)
100 120
ERROR AMP FREQUENCY RESPONSE
70
GAIN
0MAX5003-07
60 -20
50 -40
40 -60
PHASE
30 -80
20 -100
10 -120
0 -140
-10 -160
-20
0.1k
1k 10k 100k 1M
FREQUENCY (Hz)
-180
10M
V+ INPUT CURRENT vs. TEMPERATURE
2.50
2.00
1.50
1.00
0.50 VCON = VCOMP = VFB
SWITCHING
V+ = 110V
0
-40 -20 0 20 40 60
TEMPERATURE (°C)
80 100
SWITCHING FREQUENCY AND PERIOD
vs. RFREQ
400 40MAX5003-08
350
FREQUENCY
300
30
250
PERIOD
200 20
150
100 10
50
00
0 100 200 300 400 500
RFREQ (kΩ)
MAXIMUM DUTY CYCLE vs. VINDIV
80
400kΩ
70
300kΩ
60
50 200kΩ
40
30
20
100kΩ
10
VCON CLAMPED HIGH
0
1.0 1.5 2.0
PARAMETER IS
RMAXTON
2.5 3.0
VINDIV (V)
V+ SHUTDOWN CURRENT
vs. TEMPERATURE
40
39 V+ = 110V
38
VINDIV = 0
VDD = UNCONNECTED
37
36
35
34
33
32
31
30
-40 -20
0 20 40 60
TEMPERATURE (°C)
80
100
V+ CURRENT IN BOOTSTRAPPED
OPERATION vs. TEMPERATURE
28.0
V+ = 110V
VINDIV = 1.5V
27.5
27.0
26.5
26.0
-50
0 50
TEMPERATURE (°C)
100
VCC LOAD REGULATION
10
V+ = 50V TO 110V
9
8
7
6 V+ = 12V
5 V+ = 13V
4 V+ = 14V
3 V+ = 15V
2
1 ES = UNCONNECTED
VDD = UNCONNECTED
0
0 5 10
15
ICC (mA)
20
_______________________________________________________________________________________ 5
5 Page 
High-Voltage PWM
Power-Supply Controller
capacitor (5µF to 10µF) at the VCC pin, since the rail will
not support such a load. It is this current, equivalent to
the product of the total gate switching charge (from the
N-channel MOSFET data sheet), times the operating
frequency, that determines the bulk of the MAX5003
power dissipation.
The driver can source up to 560mA and sink up to 1A
transient current with a typical on source resistance of
4Ω. The no-load output levels are VCC and PGND.
Applications Information
Compensation and Loop
Design Considerations
The circuit shown in Figure 2 is essentially an energy
pump. It stores energy in the magnetic core and the air
gap of the transformer while the power switch is on,
and delivers it to the load during the off phase. It can
operate in two modes: continuous and discontinuous.
In discontinuous mode, all the energy is given to the
load before the next cycle begins; in continuous mode,
some energy is continuously stored in the core.
The system has four operating parameters: input volt-
age, output voltage, load current, and duty cycle. The
PWM controller senses the output voltage and the input
voltage, and keeps the output voltage regulated by
controlling the duty cycle.
The output filter in this circuit consists of the load resis-
tance and the capacitance on the output.
To study the stability of the feedback system and
design the compensation necessary for system stability
under all operating conditions, first determine the trans-
fer function. In discontinuous mode, since there is no
energy stored in the inductor at the end of the cycle,
the inductor and capacitor do not show the characteris-
tic double pole, and there is only a dominant pole
defined by the filter capacitor and the load resistance.
There is a zero at a higher frequency, defined by the
ESR of the output filter capacitor. Such a response is
easy to stabilize for a wide range of operating condi-
tions while retaining a reasonably fast loop response.
In continuous mode, the situation is different. The
inductor-capacitor combination creates a double pole,
since energy is stored in the inductor at all times. In
addition to the double pole, a right-half-plane zero
appears in the frequency response curves. This
response is not easy to compensate. It can result in
conditional stability, a complicated compensation net-
work, or very slow transient response.
To avoid the analytical and design problems of the con-
tinuous-conduction mode flyback topology and maintain
good loop response, choose a design incorporating a
discontinuous-conduction mode power stage
To keep the converter in discontinuous mode at all times,
the value of the power transformer’s primary inductance
must be calculated at minimum line voltage and maxi-
mum load, and the maximum duty cycle must be limited.
The MAX5003 has a programmable duty-cycle limit func-
tion intended for this purpose.
Design Methodology
Following is a general procedure for developing a sys-
tem:
1) Determine the requirements.
2) In free-running mode, choose the FREQ pin pro-
gramming resistor. In synchronized mode, determine
the clock frequency (fCLK).
3) Determine the transformer turns ratio, and check the
maximum duty cycle.
4) Determine the transformer primary inductance.
5) Complete the transformer specifications by listing
the primary maximum current, the secondary maxi-
mum current, and the minimum duty cycle at full
power.
6) Choose the MAXTON pin programming resistor.
7) Choose a filter capacitor.
8) Determine the compensation network.
Design Example
1) 36V < VIN < 72V, VOUT = 5V, IOUT = 1A, ripple
< 50mV, settling time ≈ 0.5ms.
2) Generally, the higher the frequency, the smaller the
transformer. A higher frequency also gives higher
system bandwidth and faster settling time. The
trade-off is lower efficiency. In this example, 300kHz
switching frequency is the choice to favor for a small
transformer. If the converter will be free running (not
externally synchronized), use the following formula to
calculate the RFREQ programming resistor:
RFREQ
=
100kHz
ƒSW
200k = 66.7kΩ
where:
RFREQ = Resistor between FREQ and ground
ƒSW = Switching frequency (300kHz)
If the converter is synchronized to an external clock,
the input frequency will be 1.2MHz. The external
clock runs at four times the desired switching fre-
quency.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX5003.PDF ] | |
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