INMP521

The DATA signal does not need to be buffered in normal use when the INMP521 microphones are placed close to the codec on the

PCB. If the INMP521 must drive the DATA signal over a long cable (>15 cm) or other large capacitive load, a digital buffer may be

needed. Use a signal buffer on the DATA line only when one microphone is in use or after the point where two microphones are

connected (see Figure 13.)

Figure 13. Buffered Connection Between Stereo INMP521 Devices and a Codec

The DATA output of each microphone in a stereo configuration cannot be individually buffered because the two buffer outputs

cannot drive a single signal line. If a buffer is used, take care to select a buffer with low propagation delay so that the timing of the

data connected to the codec is not corrupted.

When long wires are used to connect the codec to the INMP521, a 100 Ω source termination resistor can be used on the clock output

of the codec instead of a buffer to minimize signal over-shoot or ringing. Depending on the drive capability of the codec clock output,

a buffer may still be needed, as shown in Figure 13.

SLEEP MODE

The microphone enters sleep mode when the clock frequency falls below 1 kHz. In sleep mode, the microphone data output

The INMP521 enters sleep mode within 1 ms of the clock frequency falling below 1 kHz. The microphone wakes up from sleep mode

32,768 cycles after the clock becomes active. For a 2.4 MHz clock, the microphone begins to output data in 13.7 ms. The wake-up

time, as specified in Table 2, indicates the time from when the clock is enabled to when the INMP521 is consuming its specified

current.

START-UP TIME

The start-up time of the INMP521 from when the clock is active is the same as the wake-up time from sleep mode. The microphone

starts up 32,768 cycles after the clock is active.

CLOCK OUTPUT

CODEC

DATA

INMP521

INMP521

CLK

DATA INPUT

DATA

CLK

Page 14 of 20

Document Number: DS-INMP521-00

Revision: 1.0.