Features
Combination real-time clock with audio
■ Serial real-time clock (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