Datasheet MAX9700 (Maxim) - 10

MAX9700 1.2W, Low-EMI, Filterless, Class D Audio Amplifier tSW tSW tSW tSW VIN- VIN+ OUT- OUT+ tON(MIN) VOUT+ - VOUT- Figure 2. MAX9700 Output with an Input Signal Applied (SSM Mode) square wave when no signal is present. With no filter, amplifier, the output transistors act as current-steering the square wave appears across the load as a DC volt- switches and consume negligible additional power. Any age, resulting in finite load current, increasing power power loss associated with the class D output stage is consumption. When no signal is present at the input of mostly due to the I x R loss of the MOSFET on-resistance, the MAX9700, the outputs switch as shown in Figure 4. and quiescent current overhead. Because the MAX9700 drives the speaker differentially, The theoretical best efficiency of a linear amplifier is 78%; the two outputs cancel each other, resulting in no net Idle however, that efficiency is only exhibited at peak output Mode™ voltage across the speaker, minimizing power powers. Under normal operating levels (typical music consumption. reproduction levels), efficiency falls below 30%, whereas
Efficiency
the MAX9700 still exhibits >90% efficiencies under the Efficiency of a class D amplifier is attributed to the region same conditions (Figure 5). of operation of the output stage transistors. In a class D Idle Mode is a trademark of Maxim Integrated Products www.maximintegrated.com Maxim Integrated │ 10