ZHCSFB4A July 2016 – January 2024 DS90UB964-Q1
PRODUCTION DATA
The DS90UB964-Q1 is designed to support the Power-over-Coax (PoC) method of powering remote sensor systems. With this method, the power is delivered over the same medium (a coaxial cable) used for high-speed digital video data and bidirectional control and diagnostics data transmission. The method uses passive networks or filters that isolate the transmission line from the loading of the DC-DC regulator circuits and their connecting power traces on both sides of the link as shown in Figure 6-1.
The PoC networks' impedance of ≥ 1kΩ over a specific frequency band is recommended to isolate the transmission line from the loading of the regulator circuits provided good layout practices are followed and the PCB return loss requirements given in Table 6-2 are met. Higher PoC network impedance contributes to favorable insertion loss and return loss characteristics in the high-speed channel. The lower limit of the frequency band is defined as ½ of the frequency of the back channel, fBC. The upper limit of the frequency band is the frequency of the forward high-speed channel, fFC. However, the main criteria that need to be met in the total high-speed channel, which consists of a serializer PCB, a deserializer PCB, and a cable, are the insertion loss and return loss limits defined in the Total Channel Requirements (see Section 5.4.6.1), while the system is under maximum current load and extreme temperature conditions.
Figure 6-2 shows a PoC network recommended for a "2G" FPD-Link III consisting of a DS90UB913A-Q1 or DS90UB933-Q1 serializer and DS90UB964-Q1 with the bidirectional channel operating at the data rate of 2.5Mbps (½ fBC = 1.25MHz) and the forward channel operating at the data rate as high as 1.87Gbps (fFC ≈ 1GHz).
Table 6-1 lists essential components for this particular PoC network.
Count | Ref Des | Description | Part Number | MFR |
---|---|---|---|---|
1 | L1 | Inductor, 100µH, 0.310Ω max, 710mA MIN (Isat, Itemp) 7.2MHz SRF typ, 6.6mm × 6.6mm, AEC-Q200 | MSS7341-104ML | Coilcraft |
Inductor, 100µH, 0.606Ω max, 750mAMIN (Isat, Itemp) 7.2MHz SRF typ, 6.0mm × 6.0mm, AEC-Q200 | NRS6045T101MMGKV | Taiyo Yuden | ||
1 | L2 | Inductor, 4.7µH, 0.350Ω max, 700mA MIN (Isat, Itemp) 160MHz SRF typ, 3.8mm × 3.8mm, AEC-Q200 | 1008PS-472KL | Coilcraft |
Inductor, 4.7µH, 0.130Ω max, 830mA MIN (Isat, Itemp), 70MHz SRF typ, 3.2mm × 2.5mm, General Purpose | CBC3225T4R7MRV | Taiyo Yuden | ||
Inductor, 10µH, 0.288Ω max, 530mA MIN (Isat, Itemp) 30MHz SRF min, 3mm × 3mm, AEC-Q200 | LQH3NPZ100MJR | Murata | ||
1 | FB1 | Ferrite Bead, 1500kΩ at 1GHz, 0.5Ω max at DC 500mA at 85°C, SM0603, General Purpose | BLM18HE152SN1 | Murata |
Ferrite Bead, 1500kΩ at 1GHz, 0.5Ω max at DC 500mA at 85°C, SM0603, AEC-Q200 | BLM18HE152SZ1 | Murata |
Application report Sending Power over Coax in DS90UB913A Designs (SNLA224) discusses and defines the PoC networks in more detail.
In addition to the PoC network components selection, the placement and layout play a critical role as well.
The suggested characteristics for single-ended PCB traces (microstrips or striplines) for serializer or deserializer boards are detailed in Table 6-2. The effects of the PoC networks need to be accounted for when testing the traces for compliance to the suggested limits.
PARAMETER | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|
Ltrace | Single-ended PCB trace length from the device pin to the connector pin | 5 | cm | |||
Ztrace | Single-ended PCB trace characteristic impedance | 45 | 50 | 55 | Ω | |
Zcon | Connector (mounted) characteristic impedance | 40 | 50 | 62.5 | Ω | |
RL | Return Loss, S11 | ½ fBC < f < 0.1GHz | –20 | dB | ||
0.1GHz < f < 1GHz (f in GHz) | –12 + 8 × log(f) | dB | ||||
1GHz < f < fFC | –12 | dB | ||||
IL | Insertion Loss, S12 | f < 0.5GHz | –0.35 | dB | ||
f = 1GHz | –0.6 | dB |
The VPOC noise must be kept to 10mVp-p or lower on the source / deserializer side of the system. The VPOC fluctuations on the serializer side, caused by the sensor's transient current draw and the DC resistance of cables and PoC components, must be kept at minimum as well. Increasing the VPOC voltage and adding extra decoupling capacitance (> 10µF) help reduce the amplitude and slew rate of the VPOC fluctuations.