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RM0090: Reference manual - STMicroelectronics

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<strong>RM0090</strong> USB on-the-go full-speed (OTG_FS)<br />

the 5 V VBUS line. The external charge pump can be driven by any GPIO output. This is<br />

required for the OTG A-host, A-device and host-only configurations.<br />

The VBUS input ensures that valid VBUS levels are supplied by the charge pump during USB<br />

operations while the charge pump overcurrent output can be input to any GPIO pin<br />

configured to generate port interrupts. The overcurrent ISR must promptly disable the VBUS generation.<br />

The VBUS pin can be freed by disabling the VBUS sensing option. This is done by setting the<br />

NOVBUSSENS bit in the OTG_FS_GCCFG register. In this case the VBUS is considered<br />

internally to be always at VBUS valid level (5 V).<br />

Figure 359. USB host-only connection<br />

1. STMPS2141STR needed only if the application has to support a VBUS powered device. A basic power<br />

switch can be used if 5 V are available on the application board.<br />

2. VDD range is between 2 V and 3.6 V.<br />

30.6.1 SRP-capable host<br />

SRP support is available through the SRP capable bit in the global USB configuration<br />

register (SRPCAP bit in OTG_FS_GUSBCFG). With the SRP feature enabled, the host can<br />

save power by switching off the V BUS power while the USB session is suspended.<br />

The SRP host mode program model is described in detail in the A-device session request<br />

protocol) section.<br />

30.6.2 USB host states<br />

Host port power<br />

On-chip 5 V V BUS generation is not supported. For this reason, a charge pump or, if 5 V are<br />

available on the application board, a basic power switch, must be added externally to drive<br />

the 5 V V BUS line. The external charge pump can be driven by any GPIO output. When the<br />

application decides to power on V BUS using the chosen GPIO, it must also set the port<br />

power bit in the host port control and status register (PPWR bit in OTG_FS_HPRT).<br />

V BUS valid<br />

STM32F4xx<br />

STM32F4xx<br />

OSC_IN<br />

OSC_OUT<br />

GPIO<br />

GPIO+IRQ<br />

P 9<br />

PA11<br />

PA12<br />

STMPS2141STR<br />

Current limited<br />

power distribution<br />

switch (1)<br />

When HNP or SRP is enabled the VBUS sensing pin (PA9) pin should be connected to<br />

V BUS . The V BUS input ensures that valid V BUS levels are supplied by the charge pump<br />

EN<br />

Overcurrent<br />

V DD<br />

5 V Pwr<br />

VBUS<br />

Doc ID 018909 Rev 3 1028/1416<br />

DM<br />

DP<br />

V SS<br />

USB Std-A connector<br />

MS19906V3

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