Application Notes

AN11012
Using the TEA1703 to reduce standby power
Rev. 1 — 30 March 2011
Application note
Document information
Info
Content
Keywords
SMPS, TEA1703, TEA1738, TEA1753, standby power
Abstract
TEA1703 is a low power standby controller IC intended for use in SMPS
applications that require an extremely low no-load standby power. The
TEA1703 includes detection circuitry for output voltage, output power and
also switching detection circuitry. The TEA1703 integrates a switched
mode optocoupler driver which makes it possible to drive an optocoupler
with a high peak current, while keeping the required power low.
(NXP Semiconductors patent)
AN11012
NXP Semiconductors
Using the TEA1703 to reduce standby power
Revision history
Rev
Date
Description
v.1
20110330
first issue
Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
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Application note
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Using the TEA1703 to reduce standby power
1. Introduction
The number of electronic products used today in private homes and offices is constantly
increasing. Most products, such as: audio equipment, TVs, digital cable receivers,
DVD/Blu ray recorders, computers, printers, etc. consume a considerable amounts of
electrical power while on standby (when they are not in use but are still connected to the
mains supply). This not only is a waste of energy and money but also has a large impact
on the environment. Today, many products required to run in Standby mode have to
comply with requirements on energy consumption like the Energy Star 2.0 APS
requirements.
The TEA1703 is a low power standby controller IC intended to be used in SMPS
applications that require an extreme low no-load standby power. The TEA1703 includes
detection circuitry for output voltage, output power and also switching detection circuitry.
The TEA1703 integrates a switched mode optocoupler driver, which makes it possible to
drive an optocoupler with a high peak current, while keeping the required power low.
(NXP Semiconductors patent). using the TEA1703, the standby power consumption of a
SMPS is reduced to 30 mW or less.
Remark: Unless otherwise stated all values given in this application note are typical
values.
2. Scope and set-up of this application note
2.1 Scope
This application note describes the functionality of the TEA1703 standby controller and
the operation in combination with the TEA1738 and TEA1753 SMPS controllers. Detailed
application information is given on interfacing and performance optimization.
2.2 General setup of the application note
The setup of this document is made in such a way, that a section or paragraph on a
selected subject can be read as a stand-alone explanation with a minimum of cross
references to other document parts or the data sheet.
2.3 Related documents and tools
This application note gives no in depth application information on the TEA1738 or
TEA1753 SMPS controller. Application notes, data sheets, user manuals and design tools
can be found on the product pages for the TEA1703, TEA1738 and TEA1753 at
http://www.nxp.com.
3. TEA1703 features
•
•
•
•
•
AN11012
Application note
SMPS standby controller IC enabling very low power standby operation
Large input voltage range from 5 V up to 30 V
Very low supply current of 30 μA
Switched mode optocoupler driver output (NXP Semiconductors patent)
Ease of application
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Using the TEA1703 to reduce standby power
4. Pin description
Table 1.
Pin description
Symbol
Pin
Description
VCC
1
supply voltage; the supply voltage ranges from 5 V to 30 V. The
supply current is 30 μA
GND
2
ground connection
OPTO
3
optocoupler driver; open-drain output with integrated diode to pin
VCC. A coil in series with the optocoupler is used to achieve a high
current transfer ratio. Alternatively, a resistor instead of a coil can
be used.
n.c.
4, 5
not connected
SWDET
6
switch detect input; when the SMPS is not switching and the input
current is below the Ith(SWDET) threshold of 1.2 μA, this pin disables
the TEA1703.
The SWDET input can be used to prevent a reset of the latch
protection via the VINSENSE of the SMPS. This is the case with
the TEA1753.
The SWDET pin can be connected to VCC via a resistor when the
functionality is not necessary. The input is clamped at 1 Vd, 0.74 V
at 1.2 μA.
PSENSE
7
power sense input; the optocoupler pulses are enabled when the
voltage on PSENSE drops below 0.5 V. This level is reached at a
certain output power level and can be adjusted using an external
filtering network connected to pin PSENSE. Pin PSENSE has a
hysteresis of 15 mV. The input impedance is approximately
100 MΩ.
VSENSE
8
voltage sense input; the optocoupler pulses are disabled when
VSENSE drops below 1.22 V. This level is reached when the
output voltage drops to a certain level. This level can be adjusted
using a resistor divider network from the converter output to pin
VSENSE.
In Standby mode, the output voltage varies between the nominal
output voltage (i.e. the output voltage obtained during normal
operation) and the minimum output voltage adjusted which can be
as low as 5 V.
Pin VSENSE has no hysteresis but below 1.22 V and the internal
current source of 0.9 μA from VCC is switched off. The current
provides a small hysteresis across the VSENSE resistor to ground.
The input impedance (below 1.22 V) is approximately 100 MΩ.
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Using the TEA1703 to reduce standby power
5. Application diagram
Figure 1 shows the TEA1703 connections in a typical application.
R1
C3
47 Ω
220 pF
fly 1
Vout
fly 2
D1
STMS20M100ST
C1
680 μF
25 V
C2
680 μF
25 V
19.5 V
3.34 A
GND
D2
BAS21
1
R2
330 kΩ
U2-1
R4
4.7 MΩ
2
C4
47 nF
R5
360 kΩ
R3
220 kΩ
C5
100 pF
L1
10 mH
U1
VSENSE
PSENSE
R6
2.2 MΩ
SWDET
n.c.
8
1
7
2
TEA1703
6
3
5
4
VCC
GND
OPTO
n.c.
019aab497
Fig 1.
TEA1703 connections in a typical application
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Using the TEA1703 to reduce standby power
6. TEA1703 description and calculation
This section describes the TEA1703 functions and operation in a typical application.
6.1 General description
The TEA1703 is a standby controller IC that reduces the standby power of a switched
mode power supply. Standby mode operation information is obtained by sensing the
output voltage and the output power of the SMPS. The output voltage is measured at pin
VSENSE of the TEA1703 via the resistor divider R4 and R5 as shown in Figure 1. The
output power is measured at the flyback winding of the transformer via D2 and a low-pass
filter made by R2, R3 and C4 as shown in Figure 1.
The principle of output power measuring is based on SMPS converters where the output
power at low load increases with frequency, e.g. in a discontinuous conduction mode
flyback converter which has a fixed primary peak current during low load operation.
The block diagram (Figure 2) shows the VSENSE and PSENSE inputs and the
corresponding comparators. A SWDET input is added to disable Standby mode detection
e.g. when a latched protection is active. When pins VSENSE, PSENSE and SWDET have
the correct levels, the 28 kHz oscillator is enabled. The oscillator drives the MOSFET at
the OPTO pin with an on-time of 1.4 μS (4 % duty cycle). Pin OPTO drives the
optocoupler via a coil and disables the SMPS.
0.9 μA
VCC
GND
OPTO
REFERENCE
AND
SUPPLY
1
SWITCH
DETECT
3
VSENSE
1.22 V
POWER SENSE
2
8
VOLTAGE SENSE
0.5 V
1.2 μA
7
6
PSENSE
SWDET
OSCILLATOR
n.c.
5
4
n.c.
019aab498
Fig 2.
Block diagram
6.2 Standby mode operation
The Standby mode operation signals are shown in Figure 3. In Standby mode the
optocoupler pulses generated by the TEA1703 disable the SMPS and consequently the
output voltage drops. When the voltage at pin VSENSE reaches 1.22 V, the 0.9 μA current
source is switched off and VSENSE drops below 1.22 V. The small hysteresis prevents
fast on/off switching of the VSENSE comparator.
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Using the TEA1703 to reduce standby power
As the output of the VSENSE comparator is low, the optocoupler pulses are disabled and
the SMPS can restart. When the output capacitors are charged and the voltage on
PSENSE drops below 0.5 V, optocoupler pulses are generated again on the first SWDET
pulse. In a typical application the SMPS restarts every couple of minutes. This
considerably reduces the standby power consumption.
019aab499
Fig 3.
Standby mode operation
6.3 Normal operation
The transition to normal operation is shown in Figure 4. When, during Standby mode
operation, a load higher than the Standby mode power threshold is connected, the SMPS
switches to normal operation. In the example of Figure 4, a load slightly above the
standby power threshold is connected. VSENSE drops faster than during Standby mode
operation. When VSENSE reaches 1.22 V, the SMPS starts-up and remains active, as
PSENSE does not drop below the 0.5 V PSENSE comparator level.
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Using the TEA1703 to reduce standby power
019aab500
Fig 4.
Normal operation
6.4 PSENSE
At pin PSENSE the actual output power of the SMPS is measured. Pin PSENSE should
be connected to the secondary winding via a low pass filter (see Figure 1). The power
level at pin PSENSE is compared to an internal reference of 0.5 V. Pin PSENSE disables
the SMPS when the output power drops below a predefined level. The adjustment of the
Standby mode power threshold depends on the power control behavior of the SMPS. The
adjustment procedure for the TEA1738 is given in Section 7.7.1.
The adjustment procedure for the TEA1753 is given in Section 8.7.1.
6.5 VSENSE
At pin VSENSE the divided output voltage is compared to an internal reference voltage of
1.22 V. See the block diagram of Figure 2. When the comparator level is reached, an
internal current source of 0.9 μA from VCC to pin VSENSE is switched off and VSENSE
further drops below the comparator level. The hysteresis prevents fast on/off switching of
the comparator. Pin VSENSE enables the SMPS when the output voltage drops below a
predefined level. The adjustment procedure for the TEA1738 is given in Section 7.7.2.
The adjustment procedure for the TEA1753 is given in Section 8.7.2.
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Using the TEA1703 to reduce standby power
6.6 SWDET
A SMPS enters latched protection mode when an over voltage, over temperature or
output short circuit situation occurs. If a protection is triggered, the SMPS stops switching
and enters the off state. When the reason of the protection is removed, removing the
mains resets the latched protection. A reset is triggered via the VCC supply (TEA1738) or
via the VINSENSE (TEA1753).
When pin SWDET is connected to the secondary transformer winding, as shown in
Figure 1, the SWDET input can be used to prevent a reset of the latch protection via the
VINSENSE of the SMPS. Without this precaution the latch protection of the TEA1753 is
reset, as VINSENSE is forced low in Standby mode.
When the latch protection is not reset via VINSENSE but for instance via the VCC pin of
the TEA1738, pin SWDET can be connected to the VCC of the TEA1703 via a 2.2 MΩ
resistor. A VCC clamp (ZD2) as shown in Figure 5 is required.
Pin SWDET is a current controlled input. A current above the Ith(SWDET) level of 1.2 μA
enables the Standby mode via the optocoupler when VSENSE ≥ 1.22 V and PSENSE
≤ 0.5 V. Place the current limiting resistor (R31 in Figure 5, R50 in Figure 13) at pin
SWDET.
A current below the Ith(SWDET) level of 1.2 μA prevents switching from normal operation to
the Standby mode.
6.7 Optocoupler
To minimize the Standby power consumption it is necessary to keep all currents in a
SMPS application as low as possible. A high current transfer ratio type at low input
currents is recommended for the optocoupler such as the B/C version of the LTV-356T or
IS357.
To maintain the high current transfer ratio of the optocoupler, the optocoupler diode is
driven with a high current and low duty cycle. The average current and consequently, the
power consumption, is still low. The optocoupler drive is most effective when a coil in
series is used. The coil is magnetized during the short on-time of 1.4 μS and
demagnetized during a longer time via the internal diode from the OPTO pin to the VCC
pin. The use of a coil is much more efficient than the use of a series resistor where most of
the energy is lost in the resistor.
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N
1
F1
3.15 A
250 V
R26
47 Ω
3
C18
220 pF
RM10
Lp = 650 μH
2
LF1
R14
43 kΩ
R13
43 kΩ
R1
750 kΩ
CX1
0.33 μF
-
fly1
Vout
fly2
D5
STMS20M100ST
C9
C13
680 μF
25 V
+
C1
120 μF
400 V
C2
3300 pF
1 kV
F
R4
750 kΩ
10 MΩ
10 MΩ
R9
240 kΩ
F
F
ZD1
BZX84-B24
D2
SA2M
PROTECT
CTRL
RT1
TTC95204
3
C5
1 nF
C4
100 nF
OPTIMER
5
4
6
3
TEA1738
7
2
8
1
F
F
F
R21
330 Ω
U3-1
R28
330 kΩ
1
R29
0Ω
R32
4.7 MΩ
R34
n.m.
U4-1
Q1
2N7002
1
R22
n.m.
R17
1 kΩ
VCC
R30
220kΩ
D7
BAS21
2
Q1
2SK3569
C8
68 pF
GND
C20
47 nF
R23
35.7 kΩ
1%
C12
100 pF
DRIVER
R33
360 kΩ
C21
100 pF
L2
10 mH
R35
n.m.
2
F
R8
2.2 MΩ
C6
0.22 μF
C7
0.1 μF
50 V
C10
C17
0.22 μF
1 nF
R18
F
F
D4
BAS21W
F
U2
VSENSE
R19
0.18 Ω
33 kΩ
3
F
C15
100 nF
ISENSE
4
U3-2
LTV-817B
D6
BAS21
R15
4.7 Ω
F
R7
8.06 kΩ
C19
n.m.
R16
10 Ω
U1
U4-2
LTV-817B
R6
39 kΩ
R11
C3
0.22 μF
VINSENSE
Q3
BC848C
R10
D3
1N4148W
D1
1N4148
4
GND
R12
10 MΩ
R3
750 kΩ
ZD2
BZX383-B18
19.5 V
3. 34 A
C14
680 μF
25 V
PSENSE
C16
R25
R27
R31
10 nF
10 kΩ
1.5 MΩ
2.2 MΩ
F
L1
6.8 μH
SWDET
n.c.
8
1
7
2
TEA1703
6
3
5
4
VCC
GND
OPTO
n.c.
4
U5
AP431SR
5
C11
4.7 μF
50 V
F
F
R26
1.5 MΩ
C18
22 nF
R24
5.23 kΩ
1%
BC1
CY1
470 nF
F
019aab501
Typical TEA1703 and TEA1738 application
AN11012
10 of 36
© NXP B.V. 2011. All rights reserved.
Fig 5.
Using the TEA1703 to reduce standby power
Rev. 1 — 30 March 2011
All information provided in this document is subject to legal disclaimers.
2200 pF
630 V
R2
750 kΩ
R5
1 MΩ
3
1
BD1
KBP206G
LF2
T1
NXP Semiconductors
L
7. Typical TEA1703 and TEA1738 application
AN11012
Application note
INLET
AN11012
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Using the TEA1703 to reduce standby power
7.1 General description and typical application
Figure 5 shows a typical application of the TEA1738 low cost SMPS controller and the
TEA1703 Standby controller. During Standby operation, optocoupler U4 forces
VINSENSE (pin 5 of the TEA1738) low via transistor Q3. The SMPS stops switching when
the voltage on VINSENSE drops below 0.72 V.
7.2 Interfacing
To reduce standby power consumption, the AP431 reference (U4 in Figure 5) and the
resistor divider R23 and R24 are switched off in standby by means of Q1. This reduces
the standby power by 5 mW to 10 mW. The values of R26, R27 and C18 are not critical.
Resistors R26 and R27 reduce the maximum gate voltage and C18 creates a switch off
delay. See the switching signals in Figure 6. Until the output voltage reaches the minimum
value, the power consumption is minimal.
Alternatively R26 and R27 can be increased to reduce the standby power consumption.
This, however, reduces the accuracy of the output voltage because of the spread on the
reference input current of the AP431.
019aab502
Fig 6.
AP431SR voltage reference on/off switching
The standby information for the SMPS is obtained via optocoupler U4. The collector of the
optocoupler is not connected directly to pin VINSENSE but via transistor Q3. This is
necessary to comply with dark current requirements. Dark currents up to 10 μA can be
managed.
Remark: Dark current is the current that can flow through the output phototransistor when
it is turned off.
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Using the TEA1703 to reduce standby power
Zener diode ZD2 forms a VCC clamp at 18.5 V in Standby mode. This level is just below
the TEA1738’s minimum start-up voltage of 18.6 V. Without the Zener clamp the TEA1738
enters a repetitive restart mode where it consumes considerably more power. The Zener
clamp furthermore facilitates a fast restart of the SMPS, as the VCC voltage only has to be
charged from 18.5 V to 20.6 V.
During start-up VCC temporarily drops to 17 V and consequently the Zener current and
base current for Q3 is insufficient to pull VVINSENSE to ground. A bleeder resistor of 1 MΩ
in parallel with the Zener diode ZD2 makes VCC drops down to 13 V possible.
7.3 General performance
The no-load standby power at 230 V (AC) of the SMPS shown in Figure 5 is 39 mW. In
Standby mode, the output voltage varies between 19.9 V and 12.6 V. The standby power
threshold is 470 mW and the power-up time from standby to maximum load 160 ms.
7.4 Standby mode power consumption
The 39 mW Standby mode power consumption at 230 V (AC) is dissipated in:
•
•
•
•
•
X-cap, bridge rectifier and elcap, 2.5 mW
Start-up resistors R1 – R4, 32.5 mW
VINSENSE resistors R9 to R12, 3.4 mW
VCC of the TEA1738, less than 0.5 mW
VCC of the TEA1703, less than 0.5 mW
The start-up resistors are responsible for a substantial part of the Standby mode power
consumption. The resistors are chosen such that the start-up time at 115 V (AC) remains
below 3 s. The Standby mode power consumption and start-up times for different resistor
values are shown in Table 2.
Table 2.
Standby mode power dissipation and start-up times for different start-up resistors
Capacitance is 4.7 μF + 100 nF.
R1 + R2 = R3+ R8
Standby power
Start-up time
230 V (AC)
90 V (AC)
115 V (AC)
1 MΩ
55 mW
2.54 s
1.65 s
1.2 MΩ
47 mW
3s
2s
1.5 MΩ
39 mW
4s
2.6 s
1.8 MΩ
34 mW
5.2 s
3.2 s
2 MΩ
29 mW
6.7 s
4.2 s
A further reduction of the Standby mode power is possible when the startup resistors are
replaced by a charge MOSFET with active X-cap discharge. See Section 9, the VCC
charge MOSFET with active X-cap discharge.
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Using the TEA1703 to reduce standby power
7.5 Power-up behavior
When a load is connected during Standby mode, the TEA1738 has to start-up before it
can deliver full power. The start-up time (i.e. the time necessary to deliver full power)
depends on the time to charge the VCC capacitor. The charge time depends on the mains
voltage, the value of the VCC capacitance C11, and the value of the start-up resistors R1
to R4. To minimize the start-up time the VCC voltage in Standby mode is clamped at
18.5 V.
This considerably reduces the start-up time. Using the given component values and a
load current of 3.3 A, the start-up time at 90 V (AC) is 858 ms. At 230 V (AC) it is 160 ms.
See the power-up behavior shown in Figure 7a and Figure 7b.
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Using the TEA1703 to reduce standby power
019aab503
a. Power-up at 90 V (AC)
019aab504
b. Power-up at 230 V (AC)
Fig 7.
AN11012
Application note
Power-up behavior
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Using the TEA1703 to reduce standby power
7.6 Power-down behavior
Figure 8 shows the power-down behavior. When the load is disconnected, or when the
load drops below the Standby mode power threshold, the voltage at pin PSENSE drops
below 0.5 V. On the first SWDET pulse optocoupler pulses are generated, VINSENSE is
forced low and the SMPS is forced into Standby mode.
Using the TEA1738 the SWDET functionality is not necessary as the VCC clamp prevents
a reset of the latch protection. Alternatively pin SWDET can be connected to pin VCC via
a high-ohmic resistor of 2.2 MΩ.
Remark: The latched protection of the TEA1738 is reset when the voltage VCC drops
below 5 V
019aab505
Fig 8.
Power-down behavior
7.7 Adjustments
Using the component values shown in Figure 5, the power level to enter Standby mode is
470 mW and the minimum output voltage level at which the optocoupler is disabled 12.6
V. These levels can be adjusted separately. Preferably the power level is adjusted first.
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Using the TEA1703 to reduce standby power
7.7.1 Standby mode power threshold level adjustment
The power level to enter the Standby mode can be adjusted using the low-pass filter
connected to pin PSENSE.
Before adjustment, the correct Standby mode power level should be chosen.
A good choice is a power level slightly lower than the minimum power level of the
application during normal operation. For example, at a minimum power level of 300 mW,
R30 should be ≥ 430 kΩ. See the curves of Figure 9. The slight difference between
115 V (AC) and 230 V (AC) is caused by the overshoot of the Ipeak detector. The higher
Ipeak at 230 V (AC) results in a lower switching frequency and lower PSENSE voltage.
Capacitor C20 in parallel to R30 in Figure 5 reduces the ripple at PSENSE. The ripple at
PSENSE around the comparator level of 500 mV should be less than the hysteresis of
15 mV.
019aab506
1200
Output
power
to standby
(mW)
800
400
(1)
(2)
0
0
200
400
600
800
1000
R30 (kΩ)
(1) 230 V (AC).
(2) 115 V (AC).
Fig 9.
Output power to Standby mode versus R30
7.7.2 Minimum output voltage adjustment
In Standby mode, the output voltage varies between two levels. The maximum level is the
output voltage of the SMPS during normal operation. The minimum level is the output
voltage reached in Standby mode before the SMPS restarts. See Figure 10 where the
output voltage variation is shown in Standby mode for a 20 mA load at 115 V (AC) and
230 V (AC). At a higher load the SMPS switches to normal operation.
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AN11012
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Using the TEA1703 to reduce standby power
019aab507
a. 115 V (AC)
019aab508
b. 230 V (AC)
Fig 10. Output voltage variation at 20 mA in Standby mode
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Using the TEA1703 to reduce standby power
The minimum output voltage depends on the load in Standby mode. When the output load
is zero the minimum output voltage is equal to the set voltage. The set voltage is the
output voltage set with the resistor divider at pin VSENSE. See Figure 5.
When the output is loaded in Standby mode, the output voltage decreases below the set
voltage until the SMPS restarts. In that case the minimum output voltage is lower than the
set voltage. When the application of Figure 5 is loaded with 20 mA in Standby mode, the
difference between the set voltage and minimum output voltage is 6 V at 115 V (AC). See
Figure 10a. At 230 V (AC), the difference is less and about 2.1 V. At 230 V (AC) the
charge current for the VCC capacitor is higher and consequently the start-up time shorter.
7.7.2.1
Adjustment procedure at standby no-load
• Determine the minimum output voltage Vmin. For minimum standby power the
minimum output voltage should be as low as possible but above 5 V. At no load there
is hardly any difference between Vmin and the set voltage Vset
• Resistor R33 = 1.22 / (((Vmin − 1.22) / R32) + 1e−6). Alternatively the value for R33 for
can be found in Figure 11. The curve is valid for R32 = 4.7 MΩ
019aab509
16
Set
voltage
(V)
12
8
4
0
250
350
450
550
650
750
R33 (kΩ)
R32 = 4.7 MΩ.
Fig 11. Set voltage versus R33
7.7.2.2
Adjustment procedure at low standby loads
At low loads up to the Standby mode power threshold level, the minimum output voltage is
lower than the set voltage. See Figure 10 for an output load of 20 mA. To guarantee a
minimum output voltage is it necessary to adjust to a higher voltage (i.e. to the set voltage
as shown in Figure 11). The adjustment procedure is as follows:
• Make R32 = 4.7 MΩ and R33 = 360 kΩ. Now the set voltage sufficiently high; 12.6 V
• Apply the minimum mains voltage, e.g. 115 V (AC)
• Apply the maximum Standby mode load. At this load level the SMPS should not enter
normal operation. If not done already, it is important to first carry out the standby
power threshold level adjustment as described in Section 7.7.1
• Measure VOPTO, VDRIVER and VOUT using an oscilloscope as shown in Figure 10
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Using the TEA1703 to reduce standby power
• Determine the new set voltage when the minimum output voltage is not appropriate.
For minimum standby power the minimum output voltage should be as low as
possible but above 5 V. The difference, however, is slight
• Resistor R33 = 1.22 / (((Vset − 1.22) / R32) + 1e−6). Alternatively, the value for R33 for
can be found in Figure 11. The curve is valid for R32 = 4.7 MΩ
7.7.3 Choosing the right coil
When the set voltage is low, the voltage across the coil and the current through the
optocoupler might become too low to force VVINSENSE low and to disable the SMPS. In this
situation a lower self-inductance is an option.
Be careful not to exceed the maximum peak current of the optocoupler and keep in mind
that a large peak current effects the life cycle of the optocoupler and the standby power
consumption. Peak currents above 10 mA already have impact on the life cycle of the
optocoupler. The coil of 10 mH used in Figure 5 is a compromise between the maximum
peak current of 2.5 mA and the minimum drive current of 0.655 mA for the optocoupler.
The coil current and optocoupler pulses for the minimum and maximum output voltage of
5 V and 20 V are shown in Figure 12.
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Using the TEA1703 to reduce standby power
019aab510
a. Behavior at VOUT = 20 V
019aab511
b. Behavior at VOUT = 5 V
Fig 12. Coil current and optocoupler pulses
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Using the TEA1703 to reduce standby power
The peak value of the coil current is calculated using:
10 × ( V CC – V f ) × δ
I peak = ----------------------------------------------f osc × L
(1)
where:
Ipeak (mA) = peak coil current
VCC (V) = supply voltage of the TEA1703; equal to VOUT
Vf (V) = forward voltage of the optocoupler; 1.2 V
δ (%) = duty cycle of the optocoupler pulse; 4 %
fosc (Hz) = oscillator frequency, 28 kHz
L (H) = inductance of coil L2 in Figure 5, 10 mH
8. Typical application TEA1703 with the TEA1753
See Figure 13 on page 22 and Figure 14 on page 23 for a detailed overview of the typical
application.
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Using the TEA1703 to reduce standby power
F1
mains
inlet
LF1
R1
LF2
BD1
-
CX1
L1
+
R2
D1
L2
9
C1
C2
BC1
A
7
R18
12
C3
1
R6
R5
R6B
R5A
C8
R19
Q9
C5
D2
B
switch signal
R31
Q1
R42
D4
R8
R9
D3
R43
Q8
Q2
R14
R12
R13
C9
R11
R16
C6
R16A
R10
C10
R15
R22
C
R17
switch signal
C4
PFCDRIVER
R27
C25
13
FBSENSE
10
16
1
11
TEA1753
3
12
8
2
7
R29
E
C14
R23
4
6
5
GND
R3
R28
FBDRIVER
VOSENSE
9
D23A
R23A
C13
VINSENSE
PFCAUX
14 15
R45
VCC
FBAUX
FBCTRL
F
PFCCOMP
LATCH
PFCSENSE
HVS
U1
PFCTIMER
D
D5
C23
HV
R7
R26
R25
Q10
C17
4
C24
C22
R4
C21
C20
U2A-1
C19
RT2
NTC
C18
3
OPTIONAL
019aab987
Fig 13. Typical circuit diagram of the TEA1703 with the TEA1753 (part 1)
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Using the TEA1703 to reduce standby power
A
T1
2
11
VCC
8
TEA1791
C30
4
GND
1
2 4
1
3
n.c.
5
n.c.
6
n.c.
7
n.c.
SRSENSE
DRIVER
B
U3
D30
R30
R32
Q4
Vout+
7, 8
C31
R33
D50
L4
R53
C
L3
1
R51
D
R57
C52
5
C51
6
R52
C27
C29
U2A-2
R54
C28
2
9, 10
Vout-
E
U5
CY1
VSENSE
BC2
8
PSENSE
R50
SWDET
n.c.
7
1
TEA1703
2
6
3
5
4
VCC
GND
OPTO
n.c.
F
R34
R37
U2-2 1
R24
U2-1
C15
C16
Q7
R35
4
C34
2
3
C35
R36
U4
R38
D52
R55
C53
R56
019aab988
Fig 14. Typical circuit diagram of the TEA1703 with the TEA1753 (part 2)
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8.1 General description typical application
Figure 13 and Figure 14 show a typical application of the TEA1753 low cost SMPS
controller and the TEA1703 standby controller. During standby operation, optocoupler
U2A forces VINSENSE (pin 7 of the TEA1753) low. The SMPS stops switching when the
voltage on VINSENSE drops below 0.35 V (DC).
8.2 Interfacing
To reduce standby power consumption, the TL431 reference (U4 in Figure 13 and
Figure 14) and the resistor divider R37 and R38 are switched off in standby by means of
Q7. This reduces the standby power with 5 mW to 10 mW. The values of R55, R56 and
C53 are important in relation with components R51, R52 and C51, this relationship is
explained in more detail in Section 8.7.1. Resistors R55 and R56 reduce the maximum
gate voltage and C53 creates a switch off delay.
Alternatively, R37 and R38 can be increased to reduce the standby power consumption.
This, however, reduces the accuracy of the output voltage because of the spread on the
reference input current of the TL431.
VCC (pin 1)
line
R1
C13
R45
R2
R3
D1001A
D1001B
neutral
4
R1000
U2A-1
LTV-817B
R1001
(optional)
gate Q8 and Q9
3
VINSENSE (pin 7)
Q11
BC547
R4
C20
D1000
C21
R8
019aab513
Fig 15. The proposed VSENSE circuit for minimizing the influence of the dark current
The standby information for the SMPS is obtained via optocoupler U2A. The collector of
the optocoupler is not compensated for dark current. The brownout voltage can be
influenced if there is no compensation for dark current. Figure 15 shows an alternative
circuit diagram that compensates dark currents up to 10 μA. The red colored components
in Figure 15 have to be added and components R42 and R43 can be removed in
Figure 13 and Figure 14. Diode D1001A and D1001B are available in one package.
Remark: Dark current is the current flowing through the output of the phototransistor
when it is turned off.
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8.3 General performance
The no load standby power at 230 V (AC) of the SMPS shown in Figure 13 and Figure 14
is 32 mW. In standby, the output voltage varies between 19.5 V and 12.6 V. The standby
output power threshold is 190 mW. This corresponds to an output current of
approximately 10 mA. The worst-case power-up time from standby to maximum output
current is 600 ms (with C13 = 47 μF).
8.4 Standby power consumption
The 32 mW standby power at 230 V (AC) is dissipated in:
•
•
•
•
•
X-cap, bridge rectifier and elcap; 2.5 mW
VINSENSE resistors R1, R2, R3 and R4; 17 mW
Power losses TEA1753; 5.3 mW
VCC of the TEA1703, less than 0.5 mW
Recharging the output voltage; 7 mW
The VINSENSE resistors are responsible for a substantial part of the standby power
consumption.
8.5 Power-up behavior
When a load is connected in standby, the TEA1753 has to start-up before it can deliver full
power. The start-up time (i.e. the time necessary to deliver full power) depends on the
time to charge the VCC capacitor. The charge time depends on the value of the VCC
capacitance C13. The start-up time is approximately 580 ms if C13 is 47 μF; see
Figure 16.
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Using the TEA1703 to reduce standby power
CH1
CH2
CH3
CH4
019aab514
(1) CH1: Io = 5 A per division.
(2) CH2: TEA1753 VVINSENSE = 1 V per division.
(3) CH3: TEA1753 VVCC = 10 V per division.
(4) CH4: TEA1753 VO = 10 V per division.
Fig 16. Power-up behavior
8.6 Power-down behavior
Figure 17 shows the power-down behavior. An extra current is driven through optocoupler
U2 when the output current is minimized (during load-step).
The gate drive pulses of the flyback are now disabled for some time, see Figure 17. New
FBRIVER pulses are generated when Q7 switches off because of the discharged
capacitor C53, which results in a SWDET pulse detection at the TEA1703. The first
SWDET activates the OPTO output and forces the VINSENSE of the TEA1753 to drop until
the SMPS is forced into standby.
The TEA1753 does not generate new FBDRIVER pulses if it is forced into a latched
protection, see Figure 18 (system is forced into OVP by shorting the optocoupler).
Therefore the TEA1703 doesn’t activate the OPTO output in such circumstances (no
SWDET signal is detected during a latched protection).
Reset of the latched protection is possible by briefly removing the line voltage.
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Using the TEA1703 to reduce standby power
CH1
CH2
CH3
CH4
019aab515
(1) CH1: Io = 5 A per division.
(2) CH2: TEA1753 VVINSENSE = 1 V per division.
(3) CH3: TEA1753 VFBDRIVER = 10 V per division.
(4) CH4: TEA1703 VOPTO = 10 V per division.
Fig 17. Power-down behavior when load is removed
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Using the TEA1703 to reduce standby power
CH1
CH4
CH3
CH2
019aab516
Io = 55 mA
(1) CH1: VLATCH = 1 V per division.
(2) CH2: VO = 10 V per division.
(3) CH3: VOPTO = 10 V per division.
(4) CH4: VFBDRIVER = 10 V per division.
Fig 18. Power-down behavior when system is forced into a latched protection (OVP)
8.7 Adjustments
Using the component values of Figure 13 and Figure 14, the power level to enter standby
is 190 mW and the minimum output voltage level at which the optocoupler is disabled
12.6 V. These levels can be adjusted separately. Preferably, adjusted the power level first.
8.7.1 Standby power threshold level adjustment
The power level to enter the standby mode can be adjusted within a certain range.
Defining the values for these components depends mainly on the required minimum
current value at which the system goes into standby and the speed of the selected
feedback loop.
Using the circuit diagram (Figure 13 and Figure 14) a capacitance value for C51 between
the 27 nF and 100 nF is allowed, assuming that C51 is always equal to or slightly larger
than C53.
The value of R52 determines the minimum current value at which the system enters
standby. A higher resistance value for R52 results in a lower standby level current within a
certain range. Using a resistance value higher than this range can easily be recognized,
because it hardly has any impact on further reducing the standby current level.
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The value of R52 can be found when a constant output current load is applied just above
the required minimum current. The voltage across the PSENSE pin should be just above
the Vth(PSENSE) level, so keep it just above 0.5 V (DC).
8.7.2 Standby behavior during small load currents
In standby, the output voltage varies between two levels. The maximum level is the output
voltage of the SMPS during normal operation. The minimum level is the output voltage
reached in Standby mode before the SMPS restarts. Figure 19 shows the output voltage
variation in Standby mode at an output currents of 9 mA and 4.5 mA. The SMPS changes
from Standby mode into normal operation above an output current of approximately 9 mA.
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Using the TEA1703 to reduce standby power
CH1
CH2
CH4
CH3
019aab517
a. IO = 9 mA.
CH1
CH2
CH4
CH3
019aab518
b. IO = 4.5 mA
(1) CH1: TEA1753 VCC = 10 V per division.
(2) CH2: VO = 10 V per division.
(3) CH3: TEA1753 VFBDRIVER = 10 V per division.
(4) CH4: TEA1703 VOPTO = 10 V per division.
Fig 19. Output voltage variation in Standby mode at 9 mA and 4.5 mA
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The minimum output voltage depends on the load current in Standby mode but should
always be kept above the 5 V (DC). The minimum output voltage is set using the resistor
divider at pin VSENSE. The minimum output voltage is almost equal to the set voltage if
the output current is zero, but it drops slightly if the output is loaded with a small current.
Selecting a slightly higher minimum output voltage can compensate this effect.
8.7.2.1
Adjustment minimum VO in standby mode (output not loaded)
• Determine the minimum output voltage Vmin. For minimum standby power the
minimum output voltage should be as low as possible but above 5 V. At no-load there
is hardly any difference between Vmin and the set voltage Vset.
• Resistor R54 = 1.22 / (((Vmin − 1.22) / R53) + 1e−6). Alternatively the value for R54
can be found in Figure 20. The curve is valid for R53 = 4.7 MΩ
019aab519
16
Set voltage
(V)
12
8
4
0
250
350
450
550
650
750
R54 (kΩ)
R53 = 4.7 MΩ
Fig 20. Set voltage versus R54
8.7.3 Choosing the right coil
When the set voltage is low, the voltage across the coil and the current through the
optocoupler might become too low to force VINSENSE low and to disable the SMPS. In
this situation, a lower self-inductance is an option. Be careful not to exceed the maximum
peak current of the optocoupler and keep in mind that a large peak current effects the life
cycle of the optocoupler and the standby power consumption.
Remark: Peak currents above 10 mA already have impact on the life cycle of the
optocoupler.
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9. VCC charge MOSFET with active X-cap discharge
Figure 21 shows a proposal for a VCC charge MOSFET using active X-cap discharge.
The main advantages compared to the typical application shown in Figure 5 are:
• The VCC capacitor of the TEA1738 is charged using an increased charge current.
Using the values shown in Figure 21, the start-up time and power-up time is reduced
to 0.25 s at 115 V (AC) and 0.2 s at 230 V (AC).
• In standby mode, the charge MOSFET M1 is disabled. This reduces the no-load
standby power to approximately 10 mW
• When the mains supply voltage is disconnected, the X-cap Cx is actively discharged
The current source M1 only conducts when the mains is disconnected and during start-up
of the SMPS. In all other situations, M1 is switched off to save power. In Standby mode, a
low bias current maintains the loop formed by M1, U2, Q1 and the TEA1738 VCC is
controlled at 0.5 V. During power-up, VCC is quickly charged by M1 and the output voltage
is available within 0.25 s (depending on the load and mains voltage). R1 sets the current
source charge current. The values shown in Figure 21 give an average charge current of
approximately 700 μA, (the maximum clamp current on pin VCC). The maximum dark
current allowed is 1.5 μA.
Table 3 gives an overview of operating modes, the MOSFET M1 gate voltage and
VVINSENSE.
Table 3.
AN11012
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Overview of operating modes, MOSFET M1 gate voltage and VVINSENSE
SMPS operating modes
M1 gate voltage
VVINSENSE (V) typical
Start-up
high[1][3]
≥ 0.94
Running (normal operation)
low[2]
≥ 0.72
Standby
high[4]
≤ 0.72
Running in latched protection
high[1]
≥ 0.72
AC mains supply disconnected while running
high[1][3]
≥ 0.72
AC mains supply disconnected during latched
protection
high[1][3]
≥ 0.72
[1]
Gate voltage approximately 10 V higher than TEA1738 VCC.
[2]
Gate voltage equal to the TEA1738 VCC.
[3]
Initial value.
[4]
Gate voltage approximately 3.5 V higher than TEA1738 VCC.
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Using the TEA1703 to reduce standby power
N
Cx
220 nF
L
C2
100 pF
R6
22 kΩ
D5
1N4005
R2
47 MΩ
R5
47 MΩ
mains disconnect high
C12
1 nF
D6
1N4005
1N4148
flyback running low
standby low
charge MOSFET
M1
BSS127
D9
D11
R7
10 MΩ
C1
10 nF
D8
BZX84C10L
R1
10 kΩ
TEA1738 VCC
TEA1703 VCC
1N4148
U2
PC817C
L1
10 mH
TEA1703 VOPTO
Vctrl
R13
R4
620 kΩ
D10
1N4148
D7
1N4148
R8
1 MΩ
C11
10 nF
Vbus
Q4
BC847C
30 MΩ
Q1
BC847C
TEA1738 VINSENSE
Q2
BC847C
R3
300 kΩ
Q3
BC847C
R10
300 kΩ
C8
220 nF
R12
240 kΩ
GND PRIMARY
019aab720
Fig 21. VCC charge MOSFET with active X-cap discharge
10. TEA1703 with LED indicator
Figure 22 shows the TEA1703 with an optional LED indicator D3. The LED is normally ON
when the output power exceeds the standby power threshold.
The flyback pulses at Fly1 switch on Q1 via D4 and the RC network formed by C8, R12
and R13. Q1 switches on the output voltage feedback control via the AP431SR and, via
D5 and R7, the indicator LED.
When the output power demand is less than the standby power threshold, the optocoupler
pulses disable the SMPS and switch off Q1. In this situation, the optocoupler pulses drive
the LED indicator with a lower drive current at a lower intensity.
The LED indicator D3 has three SMPS states: ON, OFF and standby.
A small disadvantage of the indicator LED is the lower drive voltage for coil L1. In Standby
mode, when the output voltage drops, the drive current for the optocoupler may become
too small. In this situation, a lower value for L1 is an option, see Section 7.7.3.
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xxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxx x x x xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xx xx xxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxx x x
xxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxx xxx
C3
47 Ω
220 pF
fly1
NXP Semiconductors
AN11012
Application note
R1
Vout
fly2
D1
STMS20M100ST
C1
680 μF
25 V
C2
680 μF
25 V
19.5 V
3.34 A
GND
R2
330 kΩ
R9
35.7 kΩ
1%
R8
330 kΩ
1
R4
4.7 MΩ
1
U2-1
U3-1
2
2
C4
47 nF
R3
220 kΩ
R5
360 kΩ
L1
10 mH
C5
100 pF
R7
10 kΩ
C6
C5
100 nF
1 nF
U1
VSENSE
PSENSE
R6
2.2 MΩ
D4
BAS21
SWDET
n.c.
8
1
7
2
TEA1703
6
5
3
4
C7
R10
10 nF
10 kΩ
VCC
GND
D5
BAS21
U4
AP431SR
OPTO
R11
5.23 kΩ
1%
n.c.
Q1
2N7002
R12
1.5 MΩ
R13
1.5 MΩ
019aab521
Fig 22. TEA1703 with LED indicator
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C8
22 nF
Using the TEA1703 to reduce standby power
Rev. 1 — 30 March 2011
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LED
D3
D2
BAS21
AN11012
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Using the TEA1703 to reduce standby power
11. Legal information
11.1
Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
11.2
Disclaimers
Limited warranty and liability — Information in this document is believed to
be accurate and reliable. However, NXP Semiconductors does not give any
representations or warranties, expressed or implied, as to the accuracy or
completeness of such information and shall have no liability for the
consequences of use of such information.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is at the customer’s own risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
AN11012
Application note
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from national authorities.
Evaluation products — This product is provided on an “as is” and “with all
faults” basis for evaluation purposes only. NXP Semiconductors, its affiliates
and their suppliers expressly disclaim all warranties, whether express, implied
or statutory, including but not limited to the implied warranties of
non-infringement, merchantability and fitness for a particular purpose. The
entire risk as to the quality, or arising out of the use or performance, of this
product remains with customer.
In no event shall NXP Semiconductors, its affiliates or their suppliers be liable
to customer for any special, indirect, consequential, punitive or incidental
damages (including without limitation damages for loss of business, business
interruption, loss of use, loss of data or information, and the like) arising out
the use of or inability to use the product, whether or not based on tort
(including negligence), strict liability, breach of contract, breach of warranty or
any other theory, even if advised of the possibility of such damages.
Notwithstanding any damages that customer might incur for any reason
whatsoever (including without limitation, all damages referenced above and
all direct or general damages), the entire liability of NXP Semiconductors, its
affiliates and their suppliers and customer’s exclusive remedy for all of the
foregoing shall be limited to actual damages incurred by customer based on
reasonable reliance up to the greater of the amount actually paid by customer
for the product or five dollars (US$5.00). The foregoing limitations, exclusions
and disclaimers shall apply to the maximum extent permitted by applicable
law, even if any remedy fails of its essential purpose.
11.3
Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
GreenChip — is a trademark of NXP B.V.
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 30 March 2011
© NXP B.V. 2011. All rights reserved.
35 of 36
AN11012
NXP Semiconductors
Using the TEA1703 to reduce standby power
12. Contents
1
2
2.1
2.2
2.3
3
4
5
6
6.1
6.2
6.3
6.4
6.5
6.6
6.7
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.7.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Scope and set-up of this application note. . . . 3
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General setup of the application note . . . . . . . . 3
Related documents and tools . . . . . . . . . . . . . . 3
TEA1703 features. . . . . . . . . . . . . . . . . . . . . . . . 3
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Application diagram . . . . . . . . . . . . . . . . . . . . . 5
TEA1703 description and calculation . . . . . . . 6
General description . . . . . . . . . . . . . . . . . . . . . 6
Standby mode operation. . . . . . . . . . . . . . . . . . 6
Normal operation . . . . . . . . . . . . . . . . . . . . . . . 7
PSENSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
VSENSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
SWDET. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Optocoupler . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Typical TEA1703 and TEA1738 application . . 10
General description and typical application . . 11
Interfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
General performance . . . . . . . . . . . . . . . . . . . 12
Standby mode power consumption. . . . . . . . . 12
Power-up behavior . . . . . . . . . . . . . . . . . . . . . 13
Power-down behavior . . . . . . . . . . . . . . . . . . . 15
Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Standby mode power threshold level
adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.7.2
Minimum output voltage adjustment . . . . . . . . 16
7.7.2.1
Adjustment procedure at standby no-load . . . 18
7.7.2.2
Adjustment procedure at low standby loads . . 18
7.7.3
Choosing the right coil . . . . . . . . . . . . . . . . . . 19
8
Typical application TEA1703
with the TEA1753 . . . . . . . . . . . . . . . . . . . . . . . 21
8.1
General description typical application . . . . . . 24
8.2
Interfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.3
General performance . . . . . . . . . . . . . . . . . . . 25
8.4
Standby power consumption. . . . . . . . . . . . . . 25
8.5
Power-up behavior . . . . . . . . . . . . . . . . . . . . . 25
8.6
Power-down behavior . . . . . . . . . . . . . . . . . . . 26
8.7
Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.7.1
Standby power threshold level adjustment . . . 28
8.7.2
Standby behavior during small load currents . 29
8.7.2.1
Adjustment minimum VO in standby mode (output
not loaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.7.3
Choosing the right coil . . . . . . . . . . . . . . . . . . 31
9
VCC charge MOSFET with active X-cap
discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10
11
11.1
11.2
11.3
12
TEA1703 with LED indicator . . . . . . . . . . . . .
Legal information . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
35
35
35
35
36
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2011.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 30 March 2011
Document identifier: AN11012
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