Lit. Number
PMP15034 Test Results
3
The schematic of the ±15-V driver circuit is shown in Figure 4. the output voltage of the TLV61046A is set to 15V.
The additional charge pump circuit doubles the output voltage to approximately 30V. The NPN Q2 and PNP Q3
form a totem pole driver circuit. The Q4 and R5 form a simple level shift circuit. When PWM is high voltage, the
Q4 turns on. So the totem pole circuit outputs 0.7V. The voltage according LS2 is -14.3V. When the PWM is low
voltage, the output voltage of totem pole circuit is 29.3V. So the LS2 voltage is 14.3V.
Figure 4: ±15-V Rectangular Waveform Driver Circuit
The current flowing through R5 to ground increases the power loss of the circuit. It is suggested to minimize the
duty cycle of the PWM signal if the sound press meets the requirement.
The R6 in parallel with LS2 discharge the DC voltage at LS2 to zero after the TLV61046A is disabled.
Test Result
Figure 5 shows the startup waveform the 28-V circuit by EN signal. The device finishes startup process in 7ms. It
is suggested that the PWM input signal is 7ms later than EN high logic.
VOUT 5V/div
EN 2V/div
Figure 5: Startup at VIN=3.3V
Figure 6 shows operating waveform when the PWM input signal is 4KH with 30% duty and VIN = 3.3V. The
sounder voltage is charged to 28V when the Q1 turns on, and discharged to almost 0 V by the resistor when the
Q1 turns off
