Lightning to usb cable for usb host mode

We are developing an MFI registered accessory that will connect to the iphone using the usb protocol. The iphone will be in usb host mode. Are there existing lightning to usb 2 cable that we can use or do we need to make are own custom cable? What document should I read for guide lines for building a custom cable?

apple provide lightning connector,which support the USB host Mode

go to the MFI.APPLE.COM to download the ducument about accessory interface

Lightning to usb cable for usb host mode
 
 
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