مدار مجتمع (آی سی) آی‌سی صوتی ویژه

Product Attributes

Introduction

The SAE 800 is a single-tone, dual-tone or triple-tone gong IC designed for a very wide supply voltage range. If the oscillator is set to the fundamental frequency f₀ = 13.2 kHz for example, the IC will issue in triple-tone mode the minor and major third I²C sharp – a, corresponding to 660 Hz - 550 Hz - 440 Hz, in dual-tone mode the minor third I²C sharp, and in single-tone mode the tone I² (derived from the fundamental frequency f₀; f₁ = f₀ / 20, f₂ = f₀ / 24, f₃ = f₀ / 30). When it is not triggered, the IC is in a standby state and only draws a few μA. It comes in a compact P-DIP-8-1 or P-DSO-8-1 (SMD) package and only requires a few external components. An RC combination is needed to generate the fundamental frequency (pin R_OSC, C_OSC). The volume can be adjusted with another resistor (pin L). The loudspeaker must be connected directly between the output Q and the power supply V_S. The current-sink principle combined with an integrated thermal shutdown (with hysteresis) makes the IC overload-protected and short-circuit-protected. There are two trigger pins (E1, E2) for setting single-tone, dual-tone or triple-tone mode. Positive pulses on inputs E1 and/or E2 trigger the IC. The hold feedback in the logic has a delay of several milliseconds. After this delay has elapsed, the tone sequence is started. This prevents parasitic spikes from producing any effect on the trigger pins. This is a precision triangle oscillator with an external time constant (R x C). Capacitor C on pin C_0SC is charged by constant current to 1 V and then discharged to 0.5 V. The constant current is obtained on pin R_OSC with an external resistor R_R to ground. When the voltage on C_0SC is building up, the logic is reset at 350 mV. This always ensures that a complete tone sequence is issued. If the oscillator pin is short-circuited to GND during operation, the sequence is repeated. The logic unit contains the complete sequence control. The oscillator produces the power-on reset and the clock frequency. Single-tone, dual-tone or triple-tone operation is programmed on inputs E1 and E2. The 4-bit digital/analog converters are driven in parallel. In the event of oscillator disturbance, and after the sequence, the dominant stop output is set. By applying current to pin L, the sequence can be shortened by a factor of 30 for test purposes. The DAC converts the 4-bit words from the logic into the appropriate staircase currents with the particular tone frequency. The sum current I_I drives the following current amplifier. The loudness generator produces the DAC reference current I_L for all three tones. This requires connecting an external resistor to ground. The chip temperature is monitored by the junction control. At temperatures of more than approx. 170 °C, the stop input will switch the output current I_I to zero. The output current is enabled again once the chip has cooled down to approx. 150 °C. The current amplifier with a gain of 1600 boosts the current I_I from approx. 470 μA maximum to approx. 750 mA maximum. The output stage consists of an NPN transistor with its emitter on power GND and collector on pin Q. The current control insures that the output stage only conducts defined currents. In conjunction with the integrated thermal shutdown, this makes the configuration short-circuit-protected within wide limits. Because of the absence of feedback the circuit is also extremely stable and therefore uncritical in applications. Resistor R_L on pin L sets the output voltage swing. This assumes that the resistive component of the loudspeaker impedance R_Ω responds similarly as the resistance R_L. The output amplitude of the current I_I reaches the maximum I_Imax ≅ 3 x V_L / R_L at a time t of 2.33 s (only 3 tone mode), so R_L has to be scaled for this point.

Features

• Supply voltage range 2.8 V to 18 V
• Few external components (no electrolytic capacitor)
• 1 tone, 2 tones, 3 tones programmable
• Loudness control
• Typical standby current 1 μA
• Constant current output stage (no oscillation)
• High-efficiency power stage
• Short-circuit protection
• Thermal shutdown