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PDF ( 数据手册 , 数据表 ) IW1689

零件编号 IW1689
描述 Low-Power Off-line Digital PWM Controller
制造商 iWatt
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IW1689 数据手册, 描述, 功能
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







IW1689 pdf, 数据表
iW1689
Low-Power Off-line Digital PWM Controller
9.6 Constant Current Operation
The iW1689 has been designed to work in constant-current
mode for battery charging applications. If the output voltage
drops, but does not go below 20% of the nominal designed
value, the device operates in this mode. Note that during
soft-start, the constant current operation mode is disabled.
VNOM
CV mode
±10%
±5%
20% of
VNOM
Foldback
Output Current
ICC
Figure 9.6.1 Power Envelope
9.9 Internal Loop Compensation
The iW1689 incorporates an internal Digital Error Amplifier
with no requirement for external loop compensation. The
loop stability is guaranteed by design to provide at least 45
degrees of phase margin and –20dB of gain margin.
9.10 Voltage Protection Functions
The iW1689 includes functions that protect against input
and output overvoltage.
The input voltage is monitored by the VIN pin and the output
voltage is monitored by the VSENSE pin. If the voltage at these
pins exceed their undervoltage or overvoltage thresholds
for more than 4-8 cycles, the iW1689 will stop switching.
However, the IC will remain biased which will discharge the
VCC supply. Once VCC drops below the UVLO threshold, the
controller will reset itself and then initiate a new soft-start
cycle. The controller will continue to attempt to soft-start until
the error condition is removed.
The output voltage can be high enough to damage the
output capacitor when the feedback loop is broken. The
iW1689 uses the primary feedback only with no secondary
feedback loop. When the VSENSE pin is shorted to GND (by
shorting/open sense resistor). The controller will shut off with
6 consecutive pulses after start-up.
9.7 CCM Protection
The iW1689 is designed to operate in discontinuous
conduction (DCM) mode at a fixed frequency of 40 kHz in
both CC and CV modes. To avoid operation in continuous
conduction (CCM) mode, the iW1689 checks for the falling
edge of the VSENSE input on every cycle. If a falling edge of
VSENSE is not detected during the normal 25us period, the
switching period will be extended until the falling edge VSENSE
does occur. If the switching period reaches 75us without
VSENSE being detected, the iW1689 will immediately shut off.
9.8 PFM Mode at Light Load
The iW1689 normally operates in a fixed frequency PWM
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the load current drops below 10% of nominal, the controller
transitions to Pulse Frequency Modulation (PFM) mode.
Thereafter, the on-time will be modulated by the line voltage
and the off-time is modulated by the load current. The device
automatically returns to PWM mode when the load current
increases.
Rev 2.0
iW1689
November 7, 2012
Page 8







IW1689 equivalent, schematic
iW1689
Low-Power Off-line Digital PWM Controller
12.0 Physical Dimensions
5-Lead SOT Package
D
54
E1 E
12 3
e
e1
A1 A2 A
COPLANARITY
0.10
B
SEATING
PLANE
αL
C
Millimeters
MIN MAX
A-
1.45
A1 0.0
0.15
A2 0.90
1.30
B 0.30
0.50
C 0.08
0.22
D 2.90 BSC
E 2.80 BSC
E1 1.60 BSC
e 0.95 BSC
e1 1.90 BSC
L 0.30
0.60
α
Compliant to JEDEC Standard MO178
Controlling dimensions are in millimeters
This package is RoHS compliant, and conform to Halide free limits.
Soldering Temperature Resistance:
[a] Package is IPC/JEDEC Std 020D Moisture Sensitivity Level 1
[b] Package exceeds JEDEC Std No. 22-A111 for Solder Immersion resistance;
packages can withstand 10 s immersion @ < 270 °C
Dimension D does not include mold flash, protrusions or gate burrs. Mold flash, protrusions
or gate burrs shall not exceed 0.25 mm per end. Dimension E1 does not include interlead flash
or protrusion. Interlead flash or protrusion shall not exceed 0.25 mm per side.
The package top may be smaller than the package bottom. Dimension D and E1 are determined
at the outermost extremes of the plastic body exclusive of mold flash, tie bar burrs, gate burrs and
interlead flash, but including any mismatch between the top and bottom of the plastic body.
Figure 12.0.1. Physical dimensions, 5-lead SOT-23 package
13.0 Ordering Information
Part Number Mark
Option
iW1689-00
Bxxx
40 kHz fS
Note 1: Tape & Reel packing quantity is 3,000 units.
Package
SOT23-5L
Description
Tape & Reel1
Rev 2.0
iW1689
November 7, 2012
Page 16










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