CP3SP33SMSSLASHNOPB datasheet(145/407 Pages) TI1

145 / 407 page

(2 )/(

)

( )cos

CP3SP33

www.ti.com

SNOSCW5 – MAY 2013

20.11.6 VoIP and 3G Telephony

This application can require G.722 support with sample rates up to 16 kHz in 16-bit mode. The ADC and

DAC must be used at these rates with the compression being handled by a DSP. The delay caused by the

G.722 algorithm and FIFO depths should be minimized to ensure the group delay specifications are met.

20.12 Tuning the Compensation Filter

For unusual sample rates or where the circuit is used to drive a non-linear audio system, it is

straightforward to calculate the required compensation filter coefficients. First, replace all coefficients with

zero except C2, which should be replaced with a value of 20000 (to ensure that the output frequency

response is not limited by headroom). This eliminates the effect of the compensation filter and a frequency

sweep on the input to the DAC will produce the uncompensated response of the system. The inverse of

this response can then be used to calculate the required coefficients using the inverse discrete fourier

transform:

(5)

In which HD is the desired response (from ω up to ωcutoff), and n is the tap number. In practice, this

requires minor manual optimization of the coefficient LSBs to obtain acceptable ripple across the newly

optimized passband.

20.13 Obtaining Maximum DAC SNR

The noise floor of the DAC increases at frequencies above Fs/2 and care should be taken at sample rates

below 44.1 kHz, because this reduces SNR. For maximum SNR when the DAC is operated at 8 kHz, a

low-pass filter can be used to limit the bandwidth of the analog audio output to 4 kHz before driving a

system with wider bandwidth.

If the same DAC channel is used for both 8 kHz and 44.1/48 kHz sample rates, the 8-kHz signal can be

interpolated in software to a higher rate. This saves the component cost of the external filter at the

expense of group delay.

These modifications are not required in typical Bluetooth applications, because the signal noise floor is far

higher than the DAC noise to 20 kHz, and speaker bandwidths are not much wider than 4–6 kHz. It

becomes an issue when using digital attenuation on voice band signals before the DAC. This reduces

SNR linearly and the relative noise can become audible. It is recommended that the DAC is operated at

full dynamic range and attenuation is performed at the last stage in the analog signal path.

21 USB Controller

The dual-role USB controller may be used as either the host or the peripheral in point-to-point

communications with another USB device. The USB controller is a peripheral on the CPU core AHB bus.

An on-chip USB transceiver supports full-speed (12 Mbps) operation.

The USB controller complies with both the USB 2.0 specification (full-speed mode) and with the On-The-

Go supplement to the specification. USB On-The-Go has been introduced to provide a low-cost

connectivity solution for consumer devices such as mobile phones, PDAs, digital cameras, and MP3

players. Devices that are solely peripherals initiate transfers through a Session Request Protocol (SRP),

while dual-role devices support both SRP and Host Negotiation Protocol (HNP).

The USB controller is configured for up to seven endpoint pipes, one bidirectional pipe for Endpoint 0 and

unidirectional transmit and receive pipes for Endpoints 1, 2, and 3. The endpoints can be individually

programmed for Bulk/Interrupt or Isochronous transfers. (Whether these endpoints are used for IN

transactions or for OUT transactions at any time will depend on whether the device is currently being used

as a USB peripheral or as the host for point-to-point communications with another USB peripheral.)

USB Controller

145

Submit Documentation Feedback

Product Folder Links :CP3SP33

CP3SP33SMS/NOPB Datasheet(PDF) 145 Page - Texas Instruments

CP3SP33SMS/NOPB Datasheet(HTML) 145 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL