Pam8620, Application information – Diodes PAM8620 User Manual
Page 9
PAM8620
Document number: DSxxxxx Rev. 1 - 0
9 of 13
June 2013
© Diodes Incorporated
PAM8620
A Product Line of
Diodes Incorporated
Application Information
(cont.)
VCLAMP Capacitors
To ensure that the maximum gate-to-source voltage for the NMOS output transistors not exceeded, a internal regulators are used to clamp the
gate voltage. A 1µF capacitors must be connected from VCLAMP to ground and must be rated for at least 25V. The voltages at the VCLAMP
terminals vary with V
CC
and may not be used to power any other circuitry.
Internal Regulated 5-V Supply (AVDD)
The AVDD terminal is the output of an internally generated 5V supply, used for the oscillator, amplifier, power limit circuitry and logic control
circuitry. It requires a 0.1µF to 1µF capacitor, placed very close to the pin to Ground to keep the regulator stable. The regulator may not be used
to power any external circuitry.
Differential Input Power Limit
The differential input stage of the amplifier eliminates noises that appear on the two input lines of the channel. To use the PAM8620 with a
differential source, connect the positive lead of the audio source to the INP input and the negative lead from the audio source to the INN input.
To use the PAM8620 with a single-ended source, ac ground the INP input through a capacitor equal in value to the input capacitor on INN and
apply the audio source to the INN input. In a single-ended input application, the INP input should be acgrounded at the audio source other than
at the device input for best noise performance.
Using Low-ESR Capacitors
Low-ESR capacitors are recommended throughout this application section. A real (with respect to ideal) capacitor can be modeled simply as a
resistor in series with an ideal capacitor. The voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit. The
lower the equivalent value of this resistance the more the real capacitor behaves as an ideal capacitor.
Short-Circuit Protection
The PAM8620 has short circuit protection circuitry on the outputs to prevent damage to the device when output-to-output shorts, output-to-GND
shorts, or output-to-VCCshorts occur. Once a short-circuit is detected on the outputs, the output drive is immediately disabled. This is a latched
fault and must be reset by cycling the voltage on the SD pin to a logic low and back to the logic high state for normal operation. This will clear the
short-circuit flag and allow for normal operation if the short was removed. If the short was not removed, the protection circuitry will again activate.
Thermal Protection
Thermal protection on the PAM8620 prevents damage to the device when the internal die temperature exceeds 160°C. There is a ±15 degree
tolerance on this trip point from device to device. Once the die temperature exceeds the set thermal point, the device enters into the shutdown
state and the outputs are disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 50°C.
The device begins normal operation at this point without external system intervention.
Power Limit
The voltage at PL pin can used to limit the power to levels below that which is possible based on the supply rail. Add a resistor from PL to ground
to set the voltage at the PLIMIT pin. An external reference may also be used if tighter tolerance is required. Also add a 1µF capacitor from PL pin
to ground. The PLIMIT circuit sets a limit on the output peak-to-peak voltage. The gain of Class-D amplifier will automatic reduced if the output
power higher than setting value to make output power less than limited value and also provide good sound quality.