The ISOW7721 supports daisy chaining multiple ISOW7721 devices to achive > 110 mA load as shown in Figure 9-4. The below equation provides an estimate for the required number of ISOW7721 devices to meet a target load current.

$Number of device=\mathrm{c}\mathrm{e}\mathrm{i}\mathrm{l}⌊\frac{\mathrm{T}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\mathrm{t}\mathrm{ }\mathrm{l}\mathrm{o}\mathrm{a}\mathrm{d}\mathrm{ }\mathrm{c}\mathrm{u}\mathrm{r}\mathrm{r}\mathrm{e}\mathrm{n}\mathrm{t}-Maxiumum available load current}{0.8\mathrm{ }Maxiumum available load current}+1⌋$

Example:

Design a multi-device chaning using ISOW7721 to drive a 680 mA load for V_DD = 5 V and VSEL = 5 V.

The Maximum avaialble load current for V_DD = 5 V, and VSEL = 5 V is 100 mA from page 1.

$Number of device=\mathrm{c}\mathrm{e}\mathrm{i}\mathrm{l}⌊\frac{680-110}{0.8\mathrm{ }\left(110\right)}+1⌋=8$

From the above calculation, we need 8 ISOW7721 to drive a 680 mA load.

Follow the procedures below to configure multi-device chaining.

1. Set LF to GND1 to make a device as the leader of the daisy chain (only one leader is allowed in a daisy chain). The CC pin of the leader is configured as an output
2. Set LF to V_DD to make the other device as a follower (may use more than one follower to meet your system current requirement). The CC pin of the follower is configured as an input.
3. A voltage change on the LF pin requires a power cycling to put the device into the desired role. Please ensure that all devices are powered during multi-device chaining operation to prevent the VISOOUT pin of an unpowered device from exposing to an overvoltage condition. An unpowered device can cause the VSEL to set to GND and thus the maximum rating for its VISOOUT is 4 V. Device damage is possible if this VISOOUT pin is driven by another 5 V VISOOUT pin for an extensive long time.
4. Connect the CC pin of the leader to the CC pin of the follower (may use more than one follower) and this will allow the leader to synchronize with the follower.
5. Connect all the VISOOUT pins and VISOIN pins together for the leader and the follower(s).
6. Connect all the GISOUT pins together for the leader and the follower(s).
7. Connect all the V_DD pins together for the leader and the follower(s).
8. All the VSEL pins should be set to the same logic state.