Application Note No. 167

A pp li c at i on N ot e , R ev . 1 . 0 , O c t o be r 2 00 8
A p p li c a t i o n N o t e N o . 1 6 7
E S D P r o t e c ti o n f o r B r o a d b an d L o w N o i s e
A m p l i f i e r B G A 7 2 8 L 7 f o r P o r t a b l e a n d M ob i l e T V
A p pl i c a t i o n s
R F & P r o t e c ti o n D e v i c e s
Edition 2008-10-08
Published by
Infineon Technologies AG
81726 München, Germany
© Infineon Technologies AG 2009.
All Rights Reserved.
Legal Disclaimer
The information given in this document shall in no event be regarded as a guarantee of conditions or
characteristics (“Beschaffenheitsgarantie”). With respect to any examples or hints given herein, any typical values
stated herein and/or any information regarding the application of the device, Infineon Technologies hereby
disclaims any and all warranties and liabilities of any kind, including without limitation warranties of
non-infringement of intellectual property rights of any third party.
Information
For further information on technology, delivery terms and conditions and prices please contact your nearest
Infineon Technologies Office (www.infineon.com).
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question please contact your nearest Infineon Technologies Office.
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approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure
of that life-support device or system, or to affect the safety or effectiveness of that device or system. Life support
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be endangered.
Application Note No. 167
Application Note No. 167
Revision History: 2008-10-08, Rev. 1.0
Previous Version:
Page
Subjects (major changes since last revision)
Application Note
3
Rev. 1.0, 2008-10-08
Application Note No. 167
Introduction
1
Introduction
This application note shows how Infineon’s broadband low noise amplifier BGA728L7 for portable and mobile TV
applications can be protected from electrostatic discharges (ESD). Due to high electrostatic charging voltages of
several kilovolt, ESD events can result in dielectric breakdown of insulating surfaces and do damage to
electronics. The integrated on-chip protection of BGA728L7 results in an ESD hardness of at least 1kV according
to the human body model (HBM), which effectively protects the sensitive RF input transistor during manufacturing
where stringent measures are taken to minimize the risk of damage from ESD. However, in the field electrostatic
charging voltages much higher than 1 kV occur every day. Since the RF input pin of BGA728L7 is directly
connected through a DC blocking capacitor to the antenna, there is a need for additional ESD protection to
minimize the risk of damage from ESD events during daily use.
BGA728L7 covers the frequency range from 170 MHz to 1675 MHz for worldwide mobile broadcast TV services,
which operate in the following frequency bands:
•
•
•
VHF III band, 170 MHz to 230 MHz
UHF band, 470 MHz to 860 MHz
L band
– 1452 MHz to 1492 MHz (Europe)
– 1670 MHz to 1675 MHz (U.S.)
Due to the high operating frequency of up to 1.7 GHz only low-capacitive ESD protection diodes with capacitances
of less than 1 pF are suitable for ESD protection for portable and mobile TV applications. Infineon offers ESD
protection diodes with capacitances of 0.8 pF down to 0.2 pF in leadless packages of EIA case size 0503
(TSLP-4-7), 0402 (TSLP-2-17) as well as 0201 (TSSLP-2-1):
ESD0P8RFL / ESD0P4RFL
The Infineon ESD protection diodes ESD0P8RFL and ESD0P4RFL with line capacitances of 0.8 pF and 0.4 pF
respectively, come in a TSLP-4-7 package (1.2 mm x 0.8 mm x 0.39 mm) as anti-parallel configuration.
ESD0P2RF-02LRH / -02LS
The Infineon TVS diode ESD0P2RF has a line capacitance of only 0.2 pF and comes in either a TSLP-2-17
package (1 mm x 0.6 mm x 0.39 mm) or a super small TSSLP-2-1 package (0.62 mm x 0.32 mm x 0.31 mm).
ESD0P2RF is a bidirectional TVS diode with a maximum working voltage of ±5.3 V.
2
TVS Diode Concepts
Figure 1 shows two different configurations for low-capacitive ESD protection diodes to be used for RF antennas.
In the anti-parallel configuration, as shown in Figure 1 (a), either diode operates in forward biased condition, and
thus the voltage on the signal line has to range approximately between -0.3 V and +0.3 V. This is equivalent to
0dBm at an impedance of 50 Ω. For example, Infineon ESD0P4RFL with a line capacitance of 0.4 pF (this is the
total parasitic capacitance) integrates two fast switching diodes in anti-parallel configuration into one package.
Infineon ESD0P8RFL with a line capacitance of 0.8 pF is only recommended for VHF III and UHF bands, because
due to the higher capacitance noise matching is already effected in the L band.
As shown in Figure 1 (b), a further reduction of line capacitance is a bidirectional configuration. The bidirectional
configuration incorporates a TVS Zener diode and therefore the voltage on the signal line can be between -VRWM
and +VRWM (VRWM is the maximum reverse working voltage). For example, the Infineon ESD0P2RF (line
capacitance is 0.2 pF) is a bidirectional diode with a maximum reverse working voltage of 5.3 V and thus it does
not start to clip the RF signal up to power levels of at least 25 dBm at an impedance of 50 Ω. The higher clamping
voltage of the bidirectional configuration—the current from the ESD event has to flow through three diodes rather
than only one diode like in the anti-parallel configuration—results in a slightly lower ESD hardness of roughly 15 %
compared to the anti-parallel configuration.
Application Note
4
Rev. 1.0, 2008-10-08
Application Note No. 167
Application Information
-0.3 V...0 .3 V
-VRWM ...V RWM
(a) anti-parallel
XXX
(b) low cap bidirectional
TVS_diodes _concepts.vsd
Figure 1
Two different concepts for ESD protection of RF antennas: (a) two fast switching diodes in
anti-parallel configuration, (b) a combination of four fast switching diodes and one TVS Zener
diode to get a low capacitive, bidirectional TVS diode (simplified diagram)
3
Application Information
The application circuit including ESD protection diode is shown in Figure 2. The circuit is shown with bidirectional
ESD protection diode D1, however, an anti-parallel ESD protection diode can be used instead (denoted by D2 in
Figure 3). Due to the fact that the packages TSLP-4-7 and the much smaller TSSLP-2-1 are not footprint
compatible, there are two separate footprints on the PCB (see Figure 3), one for TSLP-4-7 (which can also be
used for TSLP-2-17) and one for TSSLP-2-1. For the sake of clarity it is noted that only one diode is needed, either
the bidirectional diode D1 or the anti-parallel diode D2.
The default values for C1 and L1 according to the bill of materials from the data sheet are 56 pF and 75 nH
respectively. However, 33 pF and 68 nH can be used instead, which are values from the EIA E6 series and
therefore easy and readily available. Furthermore, the E6 values result in a slightly higher gain in the VHF III band
and, in the case of using the bidirectional ESD protection diode ESD0P2RF, a slightly enhanced ESD hardness,
because of the higher impedance in the low-frequency range. The capacitance C5 is optional and only needed for
the VHF III band. It has no influence on the ESD hardness.
Please also note the design of the ground connection for the ESD protection diode in order to minimize the
inductance to ground. Ground inductance results in ringing and therefore higher peak voltage and should be kept
as small as possible.
N1
GainStep
BGA728L7
1 - GS
RFin, 50 Ω
RFout, 50 Ω
C1
RF_OUT 5
2 - RF_IN
D1
Supply
VCC - 6
L1
3
BIAS
GND 7
C4
PON - 4
PowerOn
C5
(optional)
BGA 728L7 _Blockdiagram.vsd
Figure 2
Application circuit of BGA728L7
Application Note
5
Rev. 1.0, 2008-10-08
Application Note No. 167
Application Information
X
BGA 728 L7_V2 .0_ Application_ Board.vsd
Figure 3
Application board including ESD protection
Table 1
Bill of Materials
Name
Value
Package
Manufacturer
Function
C1
56 pF (33 pF)
0402
Various
DC block
C4
1 nF
0402
Various
Supply voltage filtering
C5
1 nF
0402
Various
Optional for VHF III band
L1
75 nH (68 nH)
0402
Murata LQW15A
Bias feed
N1
BGA728L7
TSLP-7-1
Infineon
SiGe LNA
D1 (D2)
ESD0P2RF-02LS
ESD0P2RF-02LRH
ESD0P4RFL
ESD0P8RFL
TSSLP-2-1
TSLP-2-17
TSLP-4-7
TSLP-4-7
Infineon
ESD protection
C2, C3
Not used
Application Note
6
Rev. 1.0, 2008-10-08
Application Note No. 167
Typical Measurement Results
4
Typical Measurement Results
Typical electrical characteristics are summarized in Table 2. Please note that PCB and SMA connector losses
have not been subtracted from measurements results, that is measurements results of the evaluation board with
either ESD0P2RFL-02LS or ESD0P4RFL are given here. For more detailed plots of noise figure or power gain vs.
frequency please also see Figure 5 to Figure 8.
In high-gain mode the ESD protection diode should not affect noise figure or power gain too much and in low-gain
mode it should not have any affect on linearity or compression point of the LNA. Due to the low capacitance of
only 0.2 pF and 0.4 pF respectively, neither diode significantly affects power gain up to 1.8 GHz and the effect on
noise figure is less than 0.1dB in the L band. Please note that measurements results shown in Figure 4 and the
following also reflect variations in the electrical characteristics of BGA728L7, because different samples of
BGA728L7 were used for these measurements.
LNAs have usually a much lower input 1 dB compression point (IP1dB) and 3rd order input intercept point (IIP3)
than ESD protection diodes. Only in low-gain or off mode, that is when the LNA effectively operates as attenuator,
IP1dB or IIP3 could be affected by the ESD protection diode. For example, the ESD protection diode ESD0P4RFL
in anti-parallel configuration starts to clip a 900 MHz RF signal at 10 dBm (at 50 Ω) and the 3rd order intercept
point of both ESD0P4RFL and ESD0P2RF is round about 38 dBm at 900 MHz (at 50 Ω). Since both IP1dB and
IIP3 of BGA728L7 in low-gain mode are still much lower than that of the ESD protection diode, neither the antiparallel ESD0P4RFL nor the bidirectional ESD0P2RF has any affect on IP1dB or IIP3. Please note that for IIP3
measurements a frequency offset of 7 MHz was chosen, which is a typical TV channel spacing (USA, Japan:
6MHz; Australia: 7 MHz; Europe, China: 8 MHz).
ESD Testing
ESD tests were done as per IEC 61000-4-2 contact discharge, starting from 4 kV (or 1 kV in the case without ESD
protection diode) and applying 50 discharges of each polarity per test voltage. After each run of 100 contact
discharges in total, supply current of BGA728L7 was recorded and the procedure was repeated with an increased
ESD test voltage until BGA728L7 has sustained significant damage. The measurements results are plotted in
Figure 4 and for the sake of clarity measurement points related to a single sample are joined by a line.
From Figure 4 one can see that without any ESD protection diode BGA728L7 can typically withstand contact
discharges of only 2 kV and it failed already at 3 kV. Using the bidirectional ESD0P2RF-02LS for ESD protection,
ESD hardness increases to approximately 10 kV. This can be enhanced to 12 kV by using the BOM variant with
C1 = 33 pF. This is because a 33 pF capacitor has a higher impedance in the lower frequency range than a 56 pF
capacitor and thus more low-frequency energy from the ESD event is blocked and forced through the ESD
protection diode. However, using either ESD0P4RFL or ESD0P8RFL in an anti-parallel configuration, ESD
hardness can still be further enhanced to approximately 14 kV (13 kV…15 kV) for contact discharge. The test
results do not show any significant difference between both diodes and also no significant difference between
BOM variants. This is because due to the very low clamping voltage of an ESD protection diode in anti-parallel
configuration there is only little low-frequency energy that bypasses the ESD protection diode and enters the
circuit. Thus, there is only an insignificant difference between 33 pF and 56 pF. This is also the reason for the
differences in ESD hardness between ESD0P2RF-02LS and ESD0P4RFL. Since the clamping voltage of a
bidirectional diode compared to an anti-parallel configuration is always higher, there is also more low-frequency
energy that bypasses the bidirectional diode.
Highest test level defined by IEC 61000-4-2 is level 4 with 8kV test voltage for contact discharge. Thus ESD
hardness of BGA728L7 protected by either the bidirectional or an anti-parallel ESD protection diode exceeds by
far level 4. Please note that since the evaluation board has no cover at all, air discharge testing is not suggested
by IEC 61000-4-2. In any case, it would not make much sense to perform air discharge tests on the evaluation
board, because there is no antenna at all to which air discharges can be applied to.
Application Note
7
Rev. 1.0, 2008-10-08
Application Note No. 167
Typical Measurement Results
Table 2
Electrical Characteristics
TA = 25 °C; VCC = 2.8 V, VPON = 2.8 V, ZS = ZL = 50 Ω,
C1 = 33 pF, L1 = 68 pF, C5 = 1 nF, D1 = ESD0P2RF-02LS or ESD0P4RFL, unless otherwise noted
Parameter
Symbol
Values
Min.
VCC
Supply current high gain mode ICCHG
Supply current low gain mode ICCLG
High-Gain Mode: VGS = 0 V
Power gain
|S21|2
Supply voltage
Input return loss
Output return loss
1)
Noise figure
rd
Typ.
1.5
Unit
Max.
3.6
RLIN
RLOUT
NF
Note / Test Condition
V
5.5
mA
0.55
mA
15.0
dB
15.5
dB
15.5
dB
14.8
dB
14.1
dB
>10
dB
>8
dB
>8
dB
>12
dB
>14
dB
8
dB
16
dB
15
dB
11
dB
10
dB
1.4
dB
1.4
dB
1.4
dB
1.4
dB
1.5
dB
3 order input intercept point
IIP3
-7
dBm
Input 1 dB compression point
IP1dB
-9
dBm
-9
dBm
-8
dBm
VGS = 0 V
VGS = 2.8 V
f = 170 MHz
f = 470 MHz
f = 860 MHz
f = 1452 MHz
f = 1675 MHz
f = 170 MHz
f = 470 MHz
f = 860 MHz
f = 1452 MHz
f = 1675 MHz
f = 170 MHz
f = 470 MHz
f = 860 MHz
f = 1452 MHz
f = 1675 MHz
f = 170 MHz
f = 470 MHz
f = 860 MHz
f = 1452 MHz
f = 1675 MHz
f1 = 470 MHz,
f2 = 477 MHz
f = 170 MHz
f = 470 MHz
f = 1675 MHz
Low-Gain Mode: VGS = 2.8 V
3rd order input intercept point
IIP3
22
dBm
Input 1dB compression point
IP1dB
3
dBm
3.5
dBm
5
dBm
Application Note
8
f1 = 470 MHz,
f2 = 477 MHz
f = 170 MHz
f = 470 MHz
f = 1675 MHz
Rev. 1.0, 2008-10-08
Application Note No. 167
Typical Measurement Results
Table 2
Electrical Characteristics
TA = 25 °C; VCC = 2.8 V, VPON = 2.8 V, ZS = ZL = 50 Ω,
C1 = 33 pF, L1 = 68 pF, C5 = 1 nF, D1 = ESD0P2RF-02LS or ESD0P4RFL, unless otherwise noted
Parameter
Symbol
Values
Min.
Unit
Note / Test Condition
12
kV
ESD0P2RF-02LS
14
kV
ESD0P4RFL
14
kV
ESD0P8RFL
Typ.
Max.
Electrostatic Discharge
ESD hardness2)
VESD
1) Including PCB and SMA connector losses, with ESD0P2RF-02LS as ESD protection
2) As per IEC 61000-4-2 contact discharge
ESD as per IEC 61000-4-2 Contact Discharge
8
Supply Current (mA)
7
6
5
4
3
2
C1=56pF, L1=75nH, w/o D1
C1=33pF, L1=68nH, D1=ESD0P2
C1=56pF, L1=75nH, D1=ESD0P2
C1=33pF, L1=68nH, D1=ESD0P4
C1=56pF, L1=75nH, D1=ESD0P4
C1=33pF, L1=68nH, D1=ESD0P8
C1=56pF, L1=75nH, D1=ESD0P8
1
0
Figure 4
2
4
6
8
10
12
Test Voltage (pos and neg polarity, kV)
14
16
ESD hardness of BGA728L7 on evaluation board as per IEC 61000-4-2 contact discharge (50
pulses per test voltage and polarity)
Application Note
9
Rev. 1.0, 2008-10-08
Application Note No. 167
Typical Measurement Results
Noise Figure for UHF and L band w/o C5
1.9
C1=56pF, L1=75nH, w/o D1
NF (dB)
1.8
C1=56pF, L1=75nH, D1=ESD0P2
1.7
C1=33pF, L1=68nH, D1=ESD0P2
1.6
C1=33pF, L1=68nH, D1=ESD0P4
1.5
1.4
1.3
1.2
0.47 GHz
0.37
Figure 5
0.86 GHz
0.67
1.452 GHz
0.97
1.27
Frequency (GHz)
1.675 GHz
1.57
1.77
Noise figure in high gain mode without C5
Noise Figure for VHF III, UHF and L band w/C5
1.9
C1=56pF, L1=75nH, w/o D1
NF (dB)
1.8
C1=56pF, L1=75nH, D1=ESD0P2
1.7
C1=33pF, L1=68nH, D1=ESD0P2
1.6
C1=33pF, L1=68nH, D1=ESD0P4
1.5
1.4
1.3
1.2
0.23 GHz
0.17
Figure 6
0.47 GHz
0.86 GHz
0.57
0.97
Frequency (GHz)
1.452 GHz
1.37
1.675 GHz
1.77
Noise figure in high gain mode with C5
Application Note
10
Rev. 1.0, 2008-10-08
Application Note No. 167
Typical Measurement Results
Gain for UHF and L band w/o C5
19
C1=56pF, L1=75nH, w/o D1
18
C1=56pF, L1=75nH, D1=ESD0P2
C1=33pF, L1=68nH, D1=ESD0P2
Gain (dB)
17
C1=33pF, L1=68nH, D1=ESD0P4
16
15
14
13
0.47 GHz
0.37
Figure 7
0.86 GHz
0.67
1.452 GHz
0.97
1.27
Frequency (GHz)
1.675 GHz
1.57
1.77
Power gain in high gain mode without C5
Gain for VHF III, UHF and L band w/C5
19
C1=56pF, L1=75nH, w/o D1
18
C1=56pF, L1=75nH, D1=ESD0P2
C1=33pF, L1=68nH, D1=ESD0P2
Gain (dB)
17
C1=33pF, L1=68nH, D1=ESD0P4
16
15
14
13
0.23 GHz
0.17
Figure 8
0.47 GHz
0.86 GHz
0.57
0.97
Frequency (GHz)
1.452 GHz
1.37
1.675 GHz
1.77
Power gain in high gain mode with C5
Application Note
11
Rev. 1.0, 2008-10-08
Application Note No. 167
Conclusion
5
Conclusion
It was shown that Infineon’s low-capacitive ESD protection diodes with capacitances of as low as 0.2 pF are very
much suitable for ESD protection of Infineon’s wideband LNA BGA728L7 for portable and mobile TV applications,
without having a significant effect on power gain, noise figure or linearity. With each of the ESD protection diodes
discussed in this application note ESD hardness of BGA728L7 considerably exceeds the highest level defined by
IEC 61000-4-2, which is level 4 with 8 kV test voltage for contact discharge. Thus, the risk of damage from ESD
is greatly minimized and therefore the objective of safe and reliable operation can also be met in environments
where no precaution against ESD has been established.
Table 3
Infineon ESD protection diodes to be used for ESD protection of BGA728L7
Part number
Capacitance
Package
EIA size Package dimensions
Typical ESD
hardness of
BGA728L71)
ESD0P8RFL2)
0.8 pF
TSLP-4-7
0503
1.2 mm x 0.8 mm x 0.39 mm
14 kV
ESD0P4RFL
0.4 pF
TSLP-4-7
0503
1.2 mm x 0.8 mm x 0.39 mm
14 kV
0.2 pF
TSLP-2-17
0402
1.0 mm x 0.6 mm x 0.39 mm
12 kV
0.2 pF
TSSLP-2-1
0201
0.62 mm x 0.32 mm x 0.31 mm 12 kV
ESD0P2RF-02LRH
3)
ESD0P2RF-02LS
3)
1) As per IEC 61000-4-2 contact discharge
2) Not recommended for L band
3) Modified BOM with C1 = 33 pF recommended
Application Note
12
Rev. 1.0, 2008-10-08