Connecting to 8 ohms speaker

Question

Hi, 
 
 I am looking at MAX9860 as a replacement for an existing design of ours. I have few questions. 
 
 1. The current design have an 8 ohms speaker but the MAX9860 seems to be specked for 16-32 ohms speakers. Can an 8 ohms speaker be driven by MAX9860? (I guess this would load the output driver more. So I cant use max gain for DAC output?) 
 2. Is there an output over power limit function? 
 3. We use a single MEMS mic (Knowles SPH6611LR5H-1). All I have to do is AC couple this to MICLP with MICLN AC coupled to AGND? 
 
 Thanks, 
 Kay

EdSellers · Accepted Answer

Hello, Kaushalya, 
 1. The MAX9860 is intended to drive a mono headphone speaker. It is able to drive an 8&Omega; speaker, but the volume would be much lower than what can be provided by a speaker amplifier. The output will also likely become more distorted at lower power than with a 16&Omega; - 32&Omega; speaker. 
 If you look at the "HEADPHONE OUTPUT POWER vs. LOAD RESISTANCE" plot on page 9 of the datasheet, you can see that the "sweet spot" for output power is tuned for a 16&Omega; load. The output power line is illustrating the maximum power at a specific THD+N level, and the performance decreases quickly as the impedance goes below 16&Omega;. 
 2. There is no output over power limit function, because the MAX9860 cannot provide enough power to cause damage. 
 3. Yes, this is the appropriate method for using a single-ended microphone. 
 I am more familiar with legacy Maxim products so I don't have complete Analog Devices lineup information, but perhaps a CODEC with dedicated 8&Omega; speaker outputs would be more suitable for your application, like the MAX98089 or the MAX98090.)

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Connecting to 8 ohms speaker

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