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IW1689のメーカーはiWattです、この部品の機能は「Low-Power Off-line Digital PWM Controller」です。 |
部品番号 | IW1689 |
| |
部品説明 | Low-Power Off-line Digital PWM Controller | ||
メーカ | iWatt | ||
ロゴ | |||
このページの下部にプレビューとIW1689ダウンロード(pdfファイル)リンクがあります。 Total 17 pages
iW1689
Low-Power Off-line Digital PWM Controller
1.0 Features
• Primary-side feedback eliminates opto-isolators and
simplifies design
• Multi-mode operation for highest overall efficiency
• Very tight output voltage regulation
• No external compensation components required
• Complies with CEC/EPA/IEC no load power consumption
and average efficiency regulations
• Built-in secondary constant-current control with primary-
side feedback
• Low start-up current (8 µA typical)
• Built-in soft start
• Built-in short circuit protection
• AC line under/overvoltage and output overvoltage
protection
• Fixed switching frequency
• Available in a space-saving SOT-23 package
2.0 Description
The iW1689 is a high performance AC/DC power supply
controller which uses digital control technology to build
sensorless peak current mode PWM flyback power
supplies. The device provides high efficiency along with a
number of key built-in protection features while minimizing
the external component count and bill of material cost. The
iW1689 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.
The ultra-low start-up power and operating current at light
load ensure that the iW1689 is ideal for applications targeting
the newest regulatory standards for average efficiency and
standby power.
3.0 Applications
• Low power AC/DC adapter/chargers for cell phones,
PDAs, digital still cameras
• Standby supplies for televisions, DVDs, set-top boxes
and other consumer electronics
L
N
+
+ + VOUT
RTN
Rev 2.0
+
4 VCC
OUTPUT 3
GND 2
5 VIN
VSENSE 1
U1
iW1689
Figure 2.0.1 iW1689 Typical Application Circuit
iW1689
November 7, 2012
Page 1
1 Page iW1689
Low-Power Off-line Digital PWM Controller
6.0 Electrical Characteristics
VCC = 12 V, -40°C ≤ TA ≤ 85°C, unless otherwise specified (Note 1)
Parameter
Symbol Test Conditions
VIN SECTION (Pin 5)
Start-up voltage threshold
Start-up current
Shutdown low voltage threshold
Shutdown high voltage threshold
Input impedance
VINST
IIN(ST)
VUVDC
VOVDC
ZIN
TA= 25°C, positive edge
VCC = 10 V
TA= 25°C, negative edge
TA= 25°C, positive edge
iW1689-00, after start-up
VSENSE SECTION (Pin 1)
Input leakage current
Nominal voltage threshold
Output OVP threshold
OUTPUT SECTION (Pin 3)
IBVS
VSENSE(NOM)
VSENSE(MAX)
VSENSE = 2 V
iW1689-00,
TA=25°C, negative edge
TA=25°C, negative edge
Output low level ON-resistance
Output high level ON-resistance
Rise time (Note 2)
RDS(ON)LO
RDSON)HI
tR
ISINK = 5 mA
ISOURCE = 5 mA
TA = 25°C, CL = 330 pF
10% to 90%
Fall time (Note 2)
tF
TA = 25°C, CL = 330 pF
90% to 10%
Output switching frequency (Note 3)
VCC SECTION (Pin 4)
Maximum operating voltage
Start-up threshold
Undervoltage lockout threshold
Operating current
fS
iW1689-00,
ILOAD > 15% of maximum
VCC(MAX)
VCC(ST)
VCC(UVL)
ICCQ
VCC rising
iW1689-00, VCC falling
CL = 330 pF,
VSENSE = 1.5 V
Min
366
216
1.737
1.507
1.667
36
11.0
5.50
Typ
407
8
240
1.930
20
1.538
1.700
65
65
40
40
40
12.3
6.15
2.5
Max
448
12
264
2.123
1
1.569
1.734
100
100
75
75
44
16
13.6
6.80
3.5
Unit
mV
µA
mV
V
kW
μA
V
V
W
W
ns
ns
kHz
V
V
V
mA
Rev 2.0
iW1689
November 7, 2012
Page 3
3Pages iW1689
Low-Power Off-line Digital PWM Controller
9.1 Pin Detail
Pin 1 – VSENSE
Sense signal input from auxiliary winding. This provides the
secondary voltage feedback used for output regulation.
Start-up
Sequencing
VCC(ST)
Pin 2 – GND
Analog signal and power ground.
VCC
Pin 3 – OUTPUT
Gate drive signal for the external power MOSFET switch.
ENABLE
Pin 4 – VCC
Power supply for the controller during normal operation.
The controller will start up when VCC reaches 12 V (typical)
and will shut-down when the VCC voltage is 6 V (typical). A
100 nF decoupling capacitor should be connected between
the VCC pin and GND.
Pin 5 – VIN
Sense signal input representing the instantaneous rectified
line voltage at the top of the transformer primary. VIN is used
for line regulation. The input line voltage is scaled using a
resistor network. The internal impedananace is 20 kW and
the scale factor is 0.0043. It also provides input undervoltage
and overvoltage protection. This pin also provides the supply
current to the IC during start-up.
ASU
Figure 9.2.1 Start-up Sequencing Diagram
9.3 Understanding Primary Feedback
Figure 9.3.1 illustrates a simplified flyback converter. When
the switch Q1
directly drawn
frcoomndrueccttsifieddursiningustOoNid(t)v,g(tth)e. Thceurerneenrtgiyg(t)Eg(its)
is stored in the magnetizing inductance LM. The rectifying
diode D1 is reverse biased and the load current IO is
supplied by the secondary capacitor
D1 conducts and the stored energy
ECgO(.t)WishdeenliQve1retudrntos
off,
the
output.
9.2 Start-up
The iW1689 incorporates an internal soft-start function. The
soft-start time is set at 3.5 ms. Once the VIN pin voltage has
reached its turn-on threshold, the iW1689 starts switching,
but limits the on-time to a percentage of the maximum on-
time. During the first 0.5 ms, the on-time is limited to 12.5%.
During the next 1 ms, the on-time is limited to 25% and
during the last 2 ms, the on-time is limited to 50%.
If the output voltage rises above the minimum threshold
before soft-start is completed, the device assumes that the
output load is very light and immediately changes to PFM
operation.
The iW1689 will attempt to restart from any of these fault
conditions after VCC has discharged and then has recharged
to the start-up threshold.
iin(t)
vin(t)
+ ig(t)
vg(t)
–
TS(t)
N:1 id(t) VO
D1
+
CO
IO
VAUX
Q1
Figure 9.3.1 Simplified Flyback Converter
In order to regulate the output voltage within a tight
specification, the information about the output voltage and
load current needs to be accurately sensed. In the DCM
flyback converter, this information can be read via the
auxiliary winding or the primary magnetizing inductance
(LM). During the
the output filter
Q1 on-time, the load current is supplied
capacitor CO. The voltage across LM is
from
vg(t),
assuming the voltage dropped across Q1 is zero. The current
in Q1 ramps up linearly at a rate of:
dig (t) = vg (t)
dt LM
(9.1)
Rev 2.0
iW1689
November 7, 2012
Page 6
6 Page | |||
ページ | 合計 : 17 ページ | ||
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部品番号 | 部品説明 | メーカ |
IW1688 | Low Power Off Line Digital PWM Controller | iWatt |
IW1689 | Low-Power Off-line Digital PWM Controller | iWatt |