AN2031 STMICROELECTRONICS | Alldatasheet
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Technical content
1 DESCRIPTION
The STA308A is a single chip solution for digital audio processing and control in multi-channel application. It provides output capabilities for DDX (Direc t Digital Amplification). In conjunction with DDX power device, it provides high quality, high efficiency, all digital amplification. STA508 is a monolithic quad half bridge stage in Multipower BCD technology. The device can be used as dual bridge or reconfigured, by connecting CONFIG pin to Vdd pin, as single bridge with double current capability. This device is particularly designed to make the Output stage of a stereo DDX amplifier capa- ble to deliver 80 + 80W @THD = 10% at Vcc = 35V output power on 8Ω load. In single BTL configuration, is also capable to deliver a peak of 160W@THD = 10% at V cc = 35V on 4Ω load (t<= 1sec).
2 STA308-508// EVALUATI ON BOARD DESCRIPTION
In this board it is possible to solder STA308 or STA308A device how digital audio processor. There are three jumpers (JP2, JP3, JP6) to select the correct device. The board has one S/PDIF input (electrical single ended and optical). In this board it is possible to use two different powers (10V to 35V on J2) and logic (5V on J1) stages or only one supply (10V to 35V on J2) for both stages. This feature is possible setting JP1 in EXT-SEL or INT-SEL respectively. U6 and U7 are configured to drive 3 or 2 ohm (over 250W) on the channel.
2.1 SUPPLY VOLTAGE, REGULATORS
The STA308-508// board uses 5V, 3.3V power regulation for logic circuitry and 10<V cc<35 for power section of STA508 device. It is possible to apply only one power supply and to extract the logic power supply utilizing the L4971D step down device
2.2 S/PDIF INPUT INTERFACE
The STA308A controller's data interface is serial I2S for input. The STA308-508//-EVB input accommodates coaxial or optical S/PDIF digital audio interfaces using a digital audio receiver IC. Jumper JP 5 may select either input. S/PDIF interfaces (STA120D) will support sample rates from 32KHz to 96KHz Optical S/PDIF receiver IC is SHARP GP1F31R.
2.3 DIGITAL SIGNAL PROCESSING
The STA308A converts pulse code modulated, PCM, digital audio input signals into Pulse- Width Modulated PWM. This signal enters in the same time in the two STA508 ICs and the exit signal is at high level of power. The STA308 A has two independent volume control registers STA308-508 EVALUATION BOARD DESCRIPTION AN2031/0705 Rev. 1
that have an adjustment range from +48dB to -78dB in 0.5dB increments. In addition, the mat- er volume is adjustable from 0dB to -127dB in 0.5dB steps. Tone control registers boost or cut the treble and bass by +/-12dB, in 2dB steps. EQ filters are IIR biquads configurable by programmable coefficients.
2.4 POWER OUTPUT
The power level signals are applied to passive two-pole low pass filter, and provide low distor- tion audio power to the load. The output filter functions to prevent unwanted high frequency switching signals from reaching the load. Filter designs for 2 Ω. Peak voltage on power pins must not exceed 35V. Snubber networks are employed to protect the output MOSFETs from inductive transients, which can reach levels higher than the supply voltage. Output snubber filter values are R18/C66 and R14/C53. The other critical components for device reliability are C47, C51, C58, C63 (1uF) and C48, C52, C59, C64 (100nF); these bypass capacitors from Vcc and power GND pins of STA508. These capacitors must be X7R Ceramic or T antalum SMD construction and must be located as close as possible to the device pins. The STA508 shuts down when it reaches 150°C.
2.5 JUMPERS CONNECTOR
The STA308-508//-EVB provides some jumpers to configure the board.
2.5.1 JUMPERS:
JP1: (INT-SEL-EXT): short on EXT-SEL to use different power supplies; short on INT-SEL to use only one power supply; JP2: (2.5A): short (with solder tin) if STA308 IC is solder on the board. If there is the STA308A this jumper could be opened; JP3: (2.5A): short (with solder tin) if STA308 IC is solder on the board. If there is the STA308A this jumper could be opened; JP4: short this jumper to use two different power supply; JP5: (OPTIC- SPDIF -ELEC): short the central pin with ELEC pin to use Electric S/PDIF; short the central pin with OPTIC pin to use the optical S/PDIF. JP6: short (with solder tin) 3.3A and center if STA308A IC is solder on the board. If there is the STA308A this jumper could be short on 3.3V and center JP7: this pin must be open.
2.5.2 CONNECTORS:
J1: Logic supply (5V) J2: Power Supply (10V to 35V) J3: Male 20 pin connector for plug control board J4: RCA connector electric S/PDIF J5: Optical S/PDIF SHARP GP1F31R J6: Connector for output load A
3 CONFIGURE STA308A-508//- EVB WITH LPT INTERFACE
7) Run STA308A-508PContro lPanel.exe on the PC.
3.1 Configuring GUI Software:
1) Go to "Registers" page on GUI. ing SW1 button and try again. If still "failed" then make sure connections are OK. 6) Go to "Control" page on GUI. 7) Click "Ext Amp Power Up" to enable the output power. 8) Increase "ALL" master volume control.
4 PERFORMANCES
4.1 THD+Noise Ratio versus Output Powe r at different input power supply Input
Figure 1. Audio Precision
4.2 THD+Noise Ratio versus Output Powe r at different input power supply Input
Figure 2. Audio Precision
4.3 THD+Noise Ratio versus Output Powe r at different input power supply Input
Figure 3. Audio Precision
4.4 THD+Noise Ratio versus frequency at different output power Input power supply:
Figure 4. Audio Precision
5 SCHEMATIC AND LAYOUT
5.1 Schematic
Figure 5. Power Section
Figure 8. STA308A Section
Figure 9. STA508 Section Figure 10. Output Filter Section
36 GND Sub
5.2 Layout
Figure 11. Component Layer Figure 12. Solder Layer
Figure 13. Serigraphy
Table 1. Revision History
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