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USBUF
EMI filter and line termination for USB upstream ports
$0T323-6L
Figure 1. Functional diagram
33V Rt Rp
* |_|
|_| 33V t|
ey de k
D1
Grd
D2
ct
l
t i
Features e Monolithic device with recommended line termination for USB upstream ports
e Integrated Rt series termination and Ct bypassing capacitors.
e Integrated ESD protection e Small package size
Datasheet - production data
e Complies with the following standards IEC 61000-4-2, level 4 - +15 kV (air discharge) - +8 kV (contact discharge) - MIL STD 883E, Method 3015-7 - Class 3C =100 pF; R =1500Q9 - 3 positive strikes and 3 negative strikes (F =1 Hz)
Application
EMI Filter and line termination for USB upstream ports on:
e USB Hubs e PC peripherals
Description
The USB specification requires upstream ports to be terminated with pull-up resistors from the D+ and D- lines to Vbus. On the implementation of USB systems, the radiated and conducted EMI should be kept within the required levels as stated by the FCC regulations. In addition to the requirements of termination and EMC compatibility, the computing devices are required (0 be tested for ESD susceptibility.
The USBUF provides the recommended line ermination while implementing a low pass filter to imit EMI levels and providing ESD protection which exceeds IEC 61000-4-2 level 4 standard. The device is packaged in a SOT323-6L which is he smallest available lead frame package (50%
e Benefits smaller than the standard SOT23). - EMI/RFI noise suppression . Table 1. Device summa - Required line termination for USB Vv upstream ports Order codes Marking - re 2 protection exceeding IEC 61000-4-2 USBUFO1W6 UUL eve - High flexibility in the design of high density USBUFO2W6 Uu2 boards - Tailored to meet USB 1.1 standard August 2015 DoclD7041 Rev8 1/13 This is information on a product in full production. www.st.com
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Characteristics USBUF 1 Characteristics Table 2. Absolute ratings (Tamb = 25° C) Symbol Parameter Value Unit ESD discharge IEC 61000-4-2, air discharge +16 Vpp ESD discharge IEC 61000-4-2, contact discharge +9 kV ESD discharge - MIL STD 883E - Method 3015-7 +25 Tj Maximum junction temperature 150 °C Tstg Storage temperature range - 55 to +150 °C Tr Lead solder temperature (10 second duration) 260 °c Top Operating temperature range -40 to 125 °C P Power rating per resistor 100 mw Table 3. Functional diagram Rt Rp ct CODE 01 33 W 1.5 kQ 47 pF CODE 02 22 W 1.5 kQ 47 pF Tolerance +10% +10% +20% 2/13 DoclD7041 Rev 8 ky
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USBUF
Technical information
2
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Technical information
Figure 2. USB standard requirements
Full-speed or Low-speed USB Transceiver
Host or Hub port
Full-speed or Low-speed USB Transceiver
Host or
Hub port
3.3V 1.5k Rt D+ D+ Rt aL —— ee Full-speed USB Rt | Twisted pair shielded Rt Transceiver at D- Zo =900hms D- ry cer 15k( st 5m max Tt Hub 0 or i Full-speed function FULL SPEED CONNECTION 3.3V 1.5k Rt D+ D+ Rt + ctl To Low-speed USB Rt Untwisted unshielded Rt Transceiver T D- 3m max D- ry ct+ 15k 4 Tt Hub 0 or i i Low-speed function
LOW SPEED CONNECTION
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Technical information USBUF
2.1
2.2
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Application example
Figure 3. Implementation of ST solutions for USB ports
Downstream port USBDFO1W5 USBUFOIWG Upstream port m_ — D2 Gnd D1 D+ 5 D+ + Rt , CABLE % D+in| & 7Ct Rd Drout__D+;——p+ ; i d | at cet i G E ul | | Rt Rt 5 g Gnd {| —_ 33 } 3 ct Rd Du. jD- Rp 4 if? oy Rt D- D- out Fd in ou D3 av pa D FULL SPEED CONNECTION Downstream port USBDFO1W5 USBUFOIWE Upstream port [+ ——— | p+ D2 Gnd D1 5 D+ ' Rt , 8 CABLE g D+in| @ 7Ct Rd D+out__ D+; + i] II | Hy He 3 5 | Gnd ct ct E & | Rt Rt 2 g Gnd {| } 33M § 3 ct Rd D-u. jD- Rp Rt D- D- out " oul D3 33yL_1D4 D- LOW SPEED CONNECTION EMI filtering
Current FCC regulations requires that class B computing devices meet specified maximum levels for both radiated and conducted EMI.
e Radiated EMI covers the frequency range from 30 MHz to 1 GHz. e Conducted EMI covers the 450 kHz to 30 MHz range.
For the types of devices utilizing the USB, the most difficult test to pass is usually the radiated EMI test. For this reason the USBUF device is aiming to minimize radiated EMI.
The differential signal (D+ and D-) of the USB does not contribute significantly to radiated or conducted EMI because the magnetic field of both conductors cancels each other.
The inside of the PC environmentis very noisy and designers must minimize noise coupling from the different sources. D+ and D-must not be routed near high speed lines (clocks spikes).
Induced common mode noise can be minimized by running pairs of USB signals parallel to
each other and running grounded guard trace on each side of the signal pair from the USB controller to the USBUF device. If possible, locate the USBUF device physically near the
DoclD7041 Rev 8 'S7
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USBUF Technical information USB connectors. Distance between the USB controller and the USB connector must be minimized.
The 47 pF (C;) capacitors are used to bypass high frequency energy to ground and for edge control, and are placed between the driver chip and the series termination resistors (Rt). Both Ct and Rt should be placed as close to the driver chip as is practicable. The USBUF ensures a filtering protection against Electromagnetic and Radio-frequency Interferences thanks to its low-pass filter structure. This filter is characterized by the following parameters: e ~— cut-off frequency e — Insertion loss e high frequency rejection.
Figure 4. USBUF typical attenuation Figure 5. Measurement configuration
S21 (dB)
0 10 S00 TEST BOARD © MF fe =i o—_ -20 Vg ‘e) 500 -30 1 10 100 1,000 Frequency (MHz) 2.3 ESD protection
In addition to the requirements of termination and EMC compatibility, computing devices are required to be tested for ESD susceptibility. This testis described in the IEC 61000-4-2 and is already in place in Europe. This test requires that a device tolerates ESD events and remains operational without user intervention.
The USBUF is particularly optimized to perform ESD protection. ESD protection is based on the use of device which clamps at: Va =Ver +Ra-lpp
This protection function is spitted in 2 stages. As shown in Figure 6, the ESD strikes are clamped by the first stage S1 and then its remaining overvoltage is applied to the second stage through the resistor Rt. Such a configuration makes the output voltage very low at the output.
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Technical information
USBUF
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Figure 6. USBUF ESD clamping behavior
Rg Sl Rt S2 Rd , Rd y C) Vinput Rload PP Vox Voutput Ver
Device
g to be ESD Surge USBUFO1W6 protected
Figure 7. Measurement board
ESD SURGE TEST BOARD 16kV r L Air _ q 5 Discharge Vin g x 6 Vout
To have a good approximation of the remaining voltages at both Vin and Vout stages, we give the typical dynamical resistance value Rd. By taking into account these following hypothesis: Ry >Rq, Rg >Ry and Rigag > Ry, it gives these formulas:
Rg Var+Ra Vg
Rg
Vinput =
R,- Vga +Rq- Vinput
Vouput = R,
The results of the calculation done for Vg= 8 kV, Rg = 330 Q (IEC 61000-4-2 standard), Ver =/7 V (typ.) and Rg =1 Q (typ.) give: Vinput = 31.2 V Voutput =7.95 V This confirms the very low remaining voltage across the device to be protected. Itis also important to note that in this approximation the parasitic inductance effect was not taken into account. This could be few tenths of volts during few ns at the Vinput Side. This parasitic effect is not present at the Voutput Side due the low current involved after the resistance Rt. The measurements done hereafter show very clearly (figure 8) the high efficiency of the ESD protection: e no influence of the parasitic inductances on Voutput stage e Voutput clamping voltage very close to Vgr (breakdown voltage) in the positive way and - V_ (forward voltage) in the negative way
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USBUF
Technical information
2.4
2.5
Figure 8. Remaining voltage at both stages S1 (Vinput) and S2 (Voutput) during ESD surge
" Vin 50
Vout | Vout 8
Positive surge Negative surge
Please note that the USBUF is not only acting for positive ESD surges but also for negative ones. For these kinds of disturbances it clamps close to ground voltage as shown in Figure 8. (negative surge.
Latch-up phenomenon
The early aging and destruction of IC’s is often due to latch-up phenomenon which is mainly induced by dV/dt. Thanks to its structure, the USBUF provides a high immunity to latch-up phenomenon by smoothing very fast edges.
Crosstalk behavior
Figure 9. Crosstalk phenomenon
Rea Line 1 ° “| O nes Ru ] 0, Vex + By Veo J Line 2 ° L wlO Riz 1 | Oty Veo + By Ver = RECEIVERS
The crosstalk phenomenon is due to the coupling between 2 lines. The coupling factor (B12 Or Bz1) increases when the gap across lines decreases, particularly in silicon dice. In the example above the expected signal on load R_2 is o2VGz, in fact the real voltage at this point has got an extra value B21VGq. This part of the Vg signal represents the effect of the crosstalk phenomenon of the line 1 on the line 2. This phenomenon has to be taken into account when the drivers impose fast digital data or high frequency analog signals in the disturbing line. The perturbed line will be more affected if it works with low voltage signal or high load impedance (few kQ).
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Technical information USBUF
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Figure 10. Analog crosstalk Figure 11. Typical analog crosstalk measurements results Analog crosstalk (dB) 0 TEST BOARD -20 502 o [> Fur <M © -40 Vg O 500. -60 -80 y + -100 1 10 100 1,000 Frequency (MHz) Figure 10. gives the measurement circuit for the analog crosstalk application. In Figure 11.,
he curve shows the effect of the D+ cell on the D-cell. In usual frequency range of analog signals (up to 100 MHz) the effect on disturbed line is less than -37 db.
Figure 12. Digital crosstalk measurements configuration
+5V +5V soecadll L 74HC04 b+ at fino Sure D> pt Eek ° > fun Square Pulse 45 > Gal Y x Sav Generator L lo D- at > KT D3 | q Bar Veal qy Figure 12 shows the measurement circuit used to quantify the crosstalk effect in a classical
digital application.
Figure 13. Digital crosstalk results
a ¢ sear | } + Ve1
IL
i
2 §21VG1
Figure 13 shows, with a signal from 0 to 5 V and rise time of few ns, the impact on the disturbed line is less than 250 mV peak to peak. No data disturbance was noted on the other line. The measurements performed with falling edges gives an impact within the same range.
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DoclD7041 Rev 8
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USBUF
Technical information
2.6
Transition times This low pass filter has been designed in order to meet the USB 1.1 standard requirements that implies the signal edges are maintained within the 4 -20 ns stipulated USB specification limits. To verify this point, we have measured the rise time of VD+ voltage with and without the USBUF device.
Figure 15. Typical rise times with and
Figure 14. Typical rise and fall times: without protection device
measurement configuration
by rt | sy 5T] ome” | Lp b—\>— /
with
Generator j id
e— Fl 45v 5 os witholt
4y I U suncos
W fe!
4 bell fl
t
Note:
Figure 14. shows the circuit used to perform measurements of the transition times. In Figure
15., we see the results of such measurements:
tise =3.8 ns driver alone tise = 7.8 ns with protection device The adding of the protection device causes the rise time increase of roughly 4ns.
Rise time has been measured between 10% and 90% of the signal (resp. 90% and 10%)
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Packaging information USBUF 3 Packaging information Table 4. SOT323-6L Package mechanical data DIMENSIONS REF. A Millimeters Inches .~—- _, Min. | Max. | Min. | Max. i ft | A 0.8 | 1.1 | 0.031 | 0.043 e Al 0 0.1 0 | 0.004 a ES | , alg A2 | 08 | 1 | 0.031 | 0.039 H e ee er = _L b 0.15 | 0.3 | 0.006 | 0.012 AL 0.1 | 0.18 | 0.004 | 0.007 A2 D 18 2.2 0.07 0.086 1 \ Ql} d | is E 1.15 | 1.35 | 0.045 | 0.053 cS }\ ave e 0.65 Typ. 0.025 Typ. | a HE 1.8 2.4 0.07 0.094 HE L 0.1 0.4 0.004 | 0.016 Ql 0.1 0.4 0.004 | 0.016 Figure 16. Recommended footprint (dimensions in mm) i om a + a ogo 10/13 DocID7041 Rev 8 ky
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USBUF
Packaging information
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Table 5. Mechanical specifications
Lead Description Lead plating Tin-lead . . 5m min Lead plating thickness 25 m max . Sn/Pb Lead material (70% to 90%Sn) Lead coplanarity 10 m max
Body material
Molded epoxy
Flammability
UL94V-0
DoclD7041 Rev 8
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Ordering information
USBUF
4 Ordering information
Table 6. Order code
Order code Marking Package Weight Base qty Delivery mode USBUFO1W6 UU1 S0OT323-6L 5.4 mg 3000 Tape and reel USBUFO2W6 UU2 S0OT323-6L 5.4 mg 3000 Tape and reel
5 Revision history Table 7. Document revision history Date Revision Description of Changes Mar-2002 3A Last update. Feb-2005 4 Layout update. No content change. -Eoh. Operating temperature range updated to -40 to 70°C. 28-Feb-2006 5 Layout updated to current standard. 27-May-2009 6 Reformatted to the current standard. 14-} an-2014 7 Updated Section 3: Packaging information 24-Aug-2015 8 Updated Top parameter in Table 2. Minor text changes.
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USBUF
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DoclD7041 Rev 8 13/13