M41T00AUD ST串行实时时钟与音频

The M41T00AUD is a low power serial real-time clock (RTC) with an integral audio section with tone generator and 300 mW output amplifier. The RTC is a superset of the M41T00 with enhancements such as a precision reference for switchover, an oscillator fail detect circuit and storing of the time at power-down. The audio section includes a summing amplifier (inverting) at the input. An 8 kHz low pass filter follows that with a 16-step programmable gain stage next. A 256 or 512 Hz audio tone can be switched into the filter in place of the input signal. From the gain stage, the 300 mW amplifier drives the output pins.

The M41T00AUD has a built-in power sense circuit which detects power failures and automatically switches to the backup input when VCC is removed. Backup power can be supplied by a capacitor or by a battery such as a lithium coin cell. The device includes a trickle charge circuit for charging the capacitor.

The RTC includes a built-in 32.768 kHz oscillator controlled by an external crystal. Eight
register bytes are used for the clock/calendar functions and are superset compatible with the M41T00. Two additional registers control the audio section and the trickle charger. The 10 registers (see Table 2) are accessed over a 400 kHz I2C bus. The address register increments automatically after each byte READ or WRITE operation thus streamlining transfers by eliminating the need to send a new address for each by to be transferred. Typical data retention times will be in excess of 5 years with a 50 mAh 3 V lithium cell (see RTC DC characteristics, Table 12 for more information).

M41T00AUD 产品特性:

• Combination real-time clock with audio
  ■ Serial RTC based on M41T00
  ■ Audio section provides:
  – 300 mW differential audio amplifier
  – 256 and 512 Hz tone generation
  – –33 to +12 dB gain, 3 dB steps (16 steps plus MUTE)
  ■ 0°C to 70°C operation
  ■ Small DFN16 package (5 mm x 4 mm)
• Real-time clock details
  ■ Superset of M41T00
  ■ 3.0 to 3.6 V operation
  – Timekeeping down to 1.7 V
  ■ Automatic backup switchover circuit
  – Ultra low 400 nA backup current at 3.0 V (typ)
  – Suitable for battery or capacitor backup
  – On-chip trickle charge circuit for backup
  capacitor
  ■ 400 kHz I2C bus
  ■ M41T00 compatible register set with counters
  for seconds, minutes, hours, day, date, month,
  years, and century
  – Automatic leap year compensation
  – HT bit set when clock goes into backup
  mode
  ■ RTC operates using 32,768 Hz quartz crystal
  – Calibration register provides for
  adjustments of –63 to +126 ppm
  – Oscillator supports crystals with up to 40
  kΩ series resistance, 12.5 pF load
  capacitance
  ■ Oscillator fail detect circuit OF bit indicates
  when oscillator has stopped for four or more
  cycles
• Audio section
  ■ Power amplifier
  – Differential output amplifier
  – Provides 300 mW into 8 Ω
  (THD+N = 2% (max), fin = 1 kHz)
  ■ Summing node at audio input
  – Inverting configuration with summing
  resistors into the minus (-) terminal
  – 0 dB gain with 10 kΩ feedback resistor and
  20 kΩ input summing resistors
  – Signal input centered at VDD/2
  – 1.6 VP-P analog input range (max)
  ■ 256 or 512 Hz signal multiplexing with analog
  input to provide audio with beep tones
  ■ Volume control, 4-bit register
  – Allows gain adjustment from –33 dB to
  +12 dB
  – 3 dB steps
  – MUTE bit
  ■ Audio automatically shuts off in backup mode

M41T00AUD 技术支持与电子电路设计开发资源下载

1. M41T00AUD 数据手册DataSheet下载.PDF
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