ArbRider Series Digital Option

1What the digital option adds

The digital option adds parallel digital pattern outputs to the BNC ArbRider series arbitrary waveform generators, playing in lockstep with the analog channels. A single instrument then drives a device under test with its analog stimulus and the parallel digital control or data pattern that goes with it. The digital outputs are LVDS differential signals (100 Ω differential) on rear-panel mini-SAS HD connectors, and they share the instrument timebase, so each digital edge holds its position relative to the analog output. The number of outputs depends on the model and its analog channel count (Table 1).

Table 1. Digital output configurations, from each model's datasheet.

Each group of eight bits uses one rear-panel mini-SAS HD connector, so the 32-bit configurations use four. The Model 686 digital outputs are CML rather than LVDS, are offered on 4-channel models only, and are not covered by the LVDS pinout and accessory data in this note.

The digital outputs are enabled by a license key and connect through the RIDER-MINI-SAS-HD cable, a one meter cable that carries the eight LVDS pairs of one connector out of the instrument. The cable connector mates mechanically with standard mini-SAS HD hardware, but the electrical pinout is customized for the ArbRider series. Do not substitute a standard mini-SAS HD cable: it seats without trouble, but its electrical connections differ and the instrument will be damaged. Use only the RIDER-MINI-SAS-HD cable.

Two accessories convert the LVDS bus into the signal standard the bench needs, and each is ordered separately. The AT-LVDS-SMA8 is a mini-SAS to SMA adapter that breaks the eight LVDS outputs out to 16 SMA connectors, two SMA per LVDS pair. The AT-DTLL8 is a probe that connects to the RIDER-MINI-SAS-HD cable and converts the LVDS outputs to single-ended LVTTL signals.

Connecting to a custom board

To connect the RIDER-MINI-SAS-HD cable to a custom board rather than to one of the BNC accessories, use a standard mini-SAS HD receptacle such as the Amphenol 10112626-101LF, Amphenol 10112632-101LF, Amphenol 10120666-101LF, or TE Connectivity 2198484-1. The mechanical mating is standard, but the board must be wired to the custom electrical pinout of Figure 1 and the table below, not to the usual mini-SAS HD assignment. The pin map covers both the raw signal on each mini-SAS HD pin and the corresponding SMA on the AT-LVDS-SMA8 adapter.

Mini-SAS HD connector pinout

The table lists each mini-SAS HD pin, the signal assigned to it, and the matching position on the AT-LVDS-SMA8 16-SMA breakout. Pins marked reserved must not be connected.

AT-LVDS-SMA8: LVDS to 16 SMA breakout

The AT-LVDS-SMA8 cable adapter converts the mini-SAS HD connector on the instrument rear panel to 16 SMA connectors. It preserves the signal integrity and gives the flexibility needed to route the high speed digital signals from the BNC ArbRider AWG series to individual coaxial inputs. Each of the eight LVDS pairs lands on two SMA connectors, one for the positive and one for the negative leg, so the full eight-bit bus is available as differential pairs across 16 SMA. The proprietary cable is one meter long.

AT-DTLL8: LVDS to LVTTL probe

The AT-DTLL8 is an eight-bit LVDS-to-LVTTL adapter that converts the LVDS differential signals from one mini-SAS HD digital connector to single-ended LVTTL outputs (Figure 2). The output high level is programmed from software between 0.8 V and 3.8 V, for the group of eight bits. The maximum update rate depends on the programmed level: 125 Mbps at 0.8 V and 400 Mbps at 3.6 V.

AT-DTLL8 output connector

The LVTTL signals are presented on a 20-position, 2.54 mm (0.1 in), two-row IDC header (Figure 3). Channels 0 through 7 occupy eight positions, each paired with a ground, and the two remaining positions are not connected.

Choosing the right output path

The choice follows the signal standard the device under test expects. For coaxial inputs and native differential signaling at the full LVDS rate (1.54 Gbps per channel on the 685), take the LVDS bus out on the AT-LVDS-SMA8 and land each pair on its own SMA. For single-ended logic inputs, the AT-DTLL8 gives software-programmable LVTTL levels from 0.8 V to 3.8 V on a standard 0.1 in header, at up to 125 Mbps at 0.8 V and 400 Mbps at 3.6 V. In either case the digital bits stay synchronized to the analog channels through the shared instrument timebase.

Talk to an application engineer

Berkeley Nucleonics can help you specify the digital option, the RIDER-MINI-SAS-HD cable, and the AT-LVDS-SMA8 or AT-DTLL8 accessory for your ArbRider 670C, 675, or 685 configuration. Call 800-234-7858 or email info@berkeleynucleonics.com.

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