TAS5707
SLOS556–NOVEMBER 2008........................................................................................................................................................................................... www.ti.com
Overtemperature Protection
The TAS5707 has over temperature-protection system. If the device junction temperature exceeds 150°C
(nominal), the device is put into thermal shutdown, resulting in all half-bridge outputs being set in the
high-impedance (Hi-Z) state and FAULT being asserted low. The TAS5707 recovers automatically once the
temperature drops approximately 30°.
Undervoltage Protection (UVP) and Power-On
Reset (POR)
The UVP and POR circuits of the TAS5707 fully protect the device in any power-up/down and brownout situation.
While powering up, the POR circuit resets the overload circuit (OLP) and ensures that all circuits are fully
operational when the PVDD and AVDD supply voltages reach 7.6 V and 2.7 V, respectively. Although PVDD and
AVDD are independently monitored, a supply voltage drop below the UVP threshold on AVDD or either PVDD
pin results in all half-bridge outputs immediately being set in the high-impedance (Hi-Z) state and FAULT being
asserted low.
SSTIMER FUNCTIONALITY
The SSTIMER pin uses a capacitor connected between this pin and ground to control the output duty cycle when
exiting all-channel shutdown. The capacitor on the SSTIMER pin is slowly charged through an internal current
source, and the charge time determines the rate at which the output transitions from a near zero duty cycle to the
desired duty cycle. This allows for a smooth transition that minimizes audible pops and clicks. When the part is
shutdown the drivers are tristated and transition slowly down through a 3K resistor, similarly minimizing pops and
clicks. The shutdown transition time is independent of SSTIMER pin capacitance. Larger capacitors will increase
the start-up time, while capacitors smaller than 2.2 nF will decrease the start-up time. The SSTIMER pin should
be left floating for BD modulation.
CLOCK, AUTO DETECTION, AND PLL
The TAS5707 is a slave device. It accepts MCLK, SCLK, and LRCLK. The digital audio processor (DAP)
supports all the sample rates and MCLK rates that are defined in the clock control register.
The TAS5707 checks to verify that SCLK is a specific value of 32 fS, 48 fS, or 64 fS. The DAP only supports a 1 ×
fS LRCLK. The timing relationship of these clocks to SDIN is shown in subsequent sections. The clock section
uses MCLK or the internal oscillator clock (when MCLK is unstable, out of range, or absent) to produce the
internal clock (DCLK) running at 512 time the PWM switching frequency.
The DAP can autodetect and set the internal clock control logic to the appropriate settings for all supported clock
rates as defined in the clock control register.
TAS5707 has robust clock error handling that uses the bulit-in trimmed oscillator clock to quickly detect
changes/errors. Once the system detects a clock change/error, it will mute the audio (through a single step mute)
and then force PLL to limp using the internal oscillator as a reference clock. Once the clocks are stable, the
system will auto detect the new rate and revert to normal operation. During this process, the default volume will
be restored in a single step (also called hard unmute). The ramp process can be programmed to ramp back
slowly (also called soft unmute) as defined in volume register (0X0E).
SERIAL DATA INTERFACE
Serial data is input on SDIN. The PWM outputs are derived from SDIN. The TAS5707 DAP accepts serial data in
16-, 20-, or 24-bit left-justified, right-justified, and I2S serial data formats.
PWM Section
The TAS5707 DAP device uses noise-shaping and sophisticated non-linear correction algorithms to achieve high
power efficiency and high-performance digital audio reproduction. The DAP uses a fourth-order noise shaper to
increase dynamic range and SNR in the audio band. The PWM section accepts 24-bit PCM data from the DAP
and outputs two BTL PWM audio output channels.
The PWM section has individual channel dc blocking filters that can be enabled and disabled. The filter cutoff
frequency is less than 1 Hz. Individual channel de-emphasis filters for 44.1- and 48-kHz are included and can be
enabled and disabled.
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