USBUF01P6
IPAD™ EMI filter and line termination for USB upstream ports
Features
■
■
■
■
Monolithic device with recommended line
termination for USB upstream ports
Integrated R
t
series termination and C
t
bypassing capacitors.
Integrated ESD protection
Small package size
Figure 1.
SOT-666IP
Functional diagram (top view)
3.3 V
Benefits
■
■
■
■
■
Rt
D1
Ct
Rp
D4
EMI / RFI noise suppression
Required line termination for USB upstream
ports
ESD protection exceeding
IEC 61000-4-2 level 4
High flexibility in the design of high density
boards
Tailored to meet USB 2.0 standard (low speed
and full speed data transmission)
GND
3.3 V
Rt
D2
Ct
D3
Complies with the following standards:
■
IEC 61000-4-2 level4:
– 15 kV (air discharge)
– 8 kV (contact discharge)
MIL STD 883E-Method 3015-7:
– Class 3, C = 100 pF, R = 1500
Ω
– 3 positive strikes, 3 negative strikes
(F = 1 Hz)
Description
The USB specification requires upstream ports to
be terminated with pull-up resistors from the D+
and D- lines to V
bus
. For 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
to be tested for ESD susceptibility.
The USBUF01P6 provides the recommended line
termination while implementing a low pass filter to
limit EMI levels and providing ESD protection
which exceeds IEC 61000-4-2 level 4 standard.
The device is packaged in a SOT-666, which is
the smallest available lead-frame package (45%
smaller than the standard SOT323).
■
Applications
EMI Filter and line termination for USB upstream
ports on:
■
■
USB Hubs
PC peripherals
TM: IPAD is a trademeark of STMicroelectronics
February 2010
Doc ID 9883 Rev 7
1/9
www.st.com
9
Characteristics
USBUF01P6
1
Characteristics
Table 1.
Symbol
Absolute maximum rating (T
amb
= 25 °C)
Parameter
IEC 61000-4-2 air discharge
IEC 61000-4-2 contact discharge
MIL STD 883E - Method 3015-7
Value
± 16
±9
± 25
150
-55 to +150
260
-40 to + 85
Unit
V
PP
T
j
T
stg
T
L
T
op
ESD discharge
Junction temperature
Storage temperature range
kV
°C
°C
°C
°C
Maximum lead temperature for soldering during 10 s at 5 mm for case
Operating temperature range
Table 2.
Symbol
V
RM
V
BR
V
CL
I
RM
I
PP
αT
V
F
Rd
Electrical characteristics (T
amb
= 25 °C)
Parameter
Stand-off voltage
Breakdown voltage
Clamping voltage
Leakage current
Peak pulse current
Voltage temperature coefficient
Forward voltage drop
Dynamic resistance
Slope = 1/Rd
I
I
F
V
CL
V
BR
V
RM
I
RM
V
F
V
I
PP
Symbol
V
BR
I
RM
R
t
R
p
C
t
Test conditions
I
R
= 1 mA
V
RM
= 3.3 V per line
Tolerance ± 10%
Tolerance ± 10%
Tolerance ± 20%
Min.
6
Typ.
Max.
10
500
Unit
V
nA
Ω
kΩ
pF
33
1.5
47
2/9
Doc ID 9883 Rev 7
USBUF01P6
Technical information
2
Technical information
Figure 2.
USB standard requirements
3.3V
1.5k
Rt
D+
Twisted pair shielded
D+
Rt
Ct
Rt
Full-speed or
Low-speed USB
Transceiver
Ct
Rt
Full-speed USB
Transceiver
D-
Host or
Hub port
Ct
15k
15k
Zo = 90ohms
5m max
D-
Ct
Hub 0 or
Full-speed function
FULL SPEED CONNECTION
3.3V
1.5k
Rt
D+
Untwisted unshielded
D+
Rt
Ct
Rt
Full-speed or
Low-speed USB
Transceiver
Ct
Rt
Low-speed USB
Transceiver
D-
Host or
Hub port
Ct
15k
15k
3m max
D-
Ct
Hub 0 or
Low-speed function
LOW SPEED CONNECTION
2.1
Application example
Figure 3.
Implementation of ST solutions for USB ports
Downstream port
Host/Hub USB por transceivert
USBDF01W5
Rt
D+ in
Ct Rd
D+ out
USBUF01P6
D2
GND
D1
Upstream port
D+
Peripheral transceiver
D+
D+
CABLE
D+
Ct
Rt
Ct
Rt
3.3 V
Rp
Gnd
Gnd
Ct Rd
D- in
Rt
D- out
D-
D-
D-
D3
3.3V
D4
D-
FULL SPEED CONNECTION
Downstream port
Host/Hub USB por transceivert
USBDF01W5
Rt
D+ in
Ct Rd
D+ out
USBUF01P6
D2
GND
D1
Upstream port
D+
Peripheral transceiver
D+
D+
CABLE
D+
Ct
Rt
Ct
Rt
3.3 V
Rp
Gnd
Gnd
Ct Rd
D- in
Rt
D- out
D-
D-
D-
D3
3.3V
D4
D-
LOW SPEED CONNECTION
Doc ID 9883 Rev 7
3/9
Technical information
USBUF01P6
2.1.1
EMI filtering
Current FCC regulations require that class B computing devices meet specified maximum
levels for both radiated and conducted EMI.
●
●
Radiated EMI covers the frequency range from 30 MHz to 1 GHz.
Conducted EMI covers the 450 kHz to 30 MHz range.
For the types of device compliant with the USB standard, the most difficult test to pass is
usually the radiated EMI test. For this reason the USBUF01P6 device aims to minimize
radiated EMI.
The differential signal (D+ and D-) of USB devices does not contribute significantly to
radiated or conducted EMI because the magnetic field of each conductor cancels out the
other.
The inside of a PC product is very noisy and designers must minimize noise coupling from
the different sources. D+ and D- must not be routed near high speed lines (clock 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 USB connectors. Distance between
the USB controller and the USB connector must be minimized.
The 47 pF (C
t
) capacitors are used to divert high frequency energy to ground and for edge
control, and are placed between the driver chip and the series termination resistors (R
t
).
Both C
t
and R
t
should be placed as close to the driver chip as is practicable.
The USBUF01P6 ensures a filtering protection against electro-magnetic and radio
frequency Interference thanks to its low-pass filter structure. This filter is characterized by
the following parameters:
●
●
●
Cut-off frequency
Insertion loss
High frequency rejection.
Figure 5.
Measurement configuration
Figure 4.
0.00
dB
-
-2.50
-
-5.00
-
-7.50
USBUF01P6 typical attenuation
curve
50Ω
-
-10.00
-
-12.50
-
-15.00
-
-17.50
-
-20.00
-
-22.50
-
-25.00
1.0M
3.0M
10.0M
30.0M
f/Hz
100.0M
300.0M
1.0G
3.0G
TEST BOARD
UUx
Vg
50Ω
4/9
Doc ID 9883 Rev 7
USBUF01P6
Technical information
2.1.2
ESD protection
In addition to the requirements of termination and EMC compatibility, computing devices are
required to be tested for ESD susceptibility. This test is described in 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 USBUF01P6 is particularly optimized to perform ESD protection. ESD protection is
based on the use of device which clamps at:
V
CL
=
V
BR
+
R
d
⋅
I
PP
This protection function is split into 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 R
t
. Such a configuration makes the output voltage very low.
Figure 6.
USBUF01P6 ESD clamping behavior
Rg
S1
Rt
S2
Rd
V
PP
Vinput
Voutput
Rd
Rload
V
BR
V
BR
Device
to be
protected
ESD Surge
USBUF01P6
Figure 7.
Measurement board
ESD
SURGE
15kV
Air
Discharge
TEST BOARD
U
Vin
Vout
To have a good approximation of the remaining voltages at both V
input
and V
output
stages,
we give the typical dynamical resistance value R
d
. Taking into account the following
hypothesis: R
t
>R
d
, R
g
>R
d
and R
load
>R
d
, gives these formulas:
R
g
⋅
V
BR
+
R
d
⋅
V
g
Vinput
= ----------------------------------------------
-
R
g
R
t
⋅
V
BR
+
R
d
⋅
Vinput
Voutput
= ---------------------------------------------------------
-
R
t
The calculation done for V
g
= 8 kV, R
g
= 330
Ω
(IEC 61000-4-2 standard), V
BR
= 7 V (typ.)
and R
d
= 2
Ω
(typ.) gives:
V
input
= 55.48 V
V
output
= 10.36 V
Doc ID 9883 Rev 7
5/9
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