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PDF IW1707 Data sheet ( Hoja de datos )
| Número de pieza | IW1707 | |
| Descripción | Low-Power Off-Line Digital Green-Mode PWM Controller | |
| Fabricantes | iWatt | |
| Logotipo |  |
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iW1707
Low-Power Off-Line Digital Green-Mode PWM Controller
1.0 Features
2.0 Description
●● Primary-side feedback eliminates opto-isolators and
simplifies design
●● Adaptively controlled soft start enables fast and smooth
start-up for a wide range of capacitive loads (from
330 μF to 6,000 μF)
●● Active start-up scheme enables shortest possible
turn-on delay
●● Direct drive of low-cost BJT switch
●● Very tight constant voltage regulation
●● EZ-EMI ® design enhances manufacturability
●● Intrinsically low common mode noise
●● Optimized 72 kHz maximum PWM switching frequency
achieves best size and efficiency
●● Adaptive multi-mode PWM/PFM control improves
efficiency
●● Quasi-resonant operation for highest overall efficiency
●● Dynamic base current control
●● No external compensation components required
●● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
●● Built-in short circuit protection and output overvoltage
protection
●● Built-in current sense resistor short circuit protection
●● Constant current control enables output current limit and
overload protection
●● No audible noise over entire operating range
L
The iW1707 is a high performance AC/DC power supply
controller which uses digital control technology to build peak
current mode PWM flyback power supplies. The device
directly drives a power BJT and operates in quasi-resonant
mode to provide high efficiency along with a number of key
built-in protection features while minimizing the external
component count, simplifying EMI design and lowering the
total bill of material cost. The iW1707 features a distinctive
soft-start scheme, which allows for fast and yet smooth
start-up with both small and large capacitive loads. The
iW1707 removes the need for secondary feedback circuitry
while achieving excellent line and load regulation. It also
eliminates the need for loop compensation components
while maintaining stability over all operating conditions.
Pulse-by-pulse waveform analysis allows for a loop
response that is much faster than traditional solutions,
resulting in improved dynamic load response. The built-in
power limit function enables optimized transformer design
in universal off-line applications and allows for a wide input
voltage range.
iWatt’s innovative proprietary technology ensures that
power supplies built with the iW1707 can achieve both
highest average efficiency and less than 100 mW no-load
consumption, and have fast yet smooth start-up with a wide
range of capacitive loads with output voltage up to 12 V, and
are ideal for network and home appliance power supplies
applications.
3.0 Applications
●● Network power adapters for ADSL, wireless access
points, routers
●● AC/DC power supplies in home appliances
+
N
+ VOUT
GND
U1
iW1707
1 VCC
OUTPUT 6
2 VSENSE
GND 5
3 ASU
ISENSE 4
Figure 3.1: iW1707 Typical Application Circuit
(Using Depletion Mode NFET as Active Start-up Device)
Rev. 0.2
iW1707
March 8, 2012
Page 1
1 page  
iW1707
Low-Power Off-Line Digital Green-Mode PWM Controller
7.0 Typical Performance Characteristics
4.08 12.0
4.04 11.6
4.00 11.2
3.96 10.8
3.92 10.4
3.88-50 -25 0
25 50 75 100 125
Ambient Temperature (ºC)
Figure 7.1: VCC UVLO vs. Temperature
150
80
10.0-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.2: Start-Up Threshold vs. Temperature
2.010
76 2.006
72 2.002
68 1.998
64 1.994
60-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.3: Switching Frequency vs. Temperature1
2.5
1.990-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.4: Internal Reference vs. Temperature
2.0
1.5
1.0
0.5
0.00.0
3.0 6.0
VCC (V)
9.0
12.0
Figure 7.5: VCC vs. VCC Supply Start-up Current
Note:
Note 1. Operating frequency varies based on the load conditions, see Section 9.6 for more details.
Rev. 0.2
iW1707
March 8, 2012
Page 5
5 Page 
iW1707
Low-Power Off-Line Digital Green-Mode PWM Controller
9.12 Cable Drop Compensation
The iW1707 incorporates an innovative method to
compensate for any IR drop in the secondary circuitry
including cable and cable connector. A 6 W adapter with
12 V DC output has 1.26% deviation at 0.5 A load current
due to the drop across a 24 AWG, 1.8 meter DC cable
without cable compensation. The iW1707 compensates
for this voltage drop by providing a voltage offset to the
feedback signal based on the amount of load current
detected.
The “Cable Comp” specified in the Table in Section 11.0
refers to the voltage increment at PCB end from no-load
to full-load conditions in the CV mode, with the assumption
that the secondary diode voltage drop can be ignored at
the point when the secondary voltage is sensed. Also, the
“Cable Comp” is specified based on the nominal output
voltage of 5 V. For different output voltage, the actual
voltage increment needs to be scaled accordingly.
To calculate the amount of cable compensation needed,
take the resistance of the cable and connector and multiply
by the maximum output current.
Rev. 0.2
iW1707
March 8, 2012
Page 11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet IW1707.PDF ] | |
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