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onsemi FAN3852UC16X: ECM Microphone Preamplifier with Integrated PDM Output
9/23/2026 1:46:43 AM
The FAN3852UC16X from onsemi is a highly integrated microphone preamplifier designed to convert the analog output of an electret condenser microphone (ECM) into a digital pulse density modulation (PDM) data stream. The chip integrates a preamplifier, a low-dropout regulator (LDO), and an oversampling Sigma-Delta ADC in a 6-pin WLCSP package measuring only 1.24 mm × 0.84 mm. For TWS earbuds, smart watches, and portable recording devices, it provides a complete signal chain from analog sound pickup to digital output in a single chip.Core Specifications at a Glance
|
Parameter |
Specification |
|
Function |
ECM microphone preamplifier + PDM output |
|
Supply voltage |
1.64 V to 3.63 V |
|
Typical operating current |
420 µA |
|
Sleep mode current |
1.5 µA |
|
Normal operating power |
0.85 mW |
|
Signal-to-noise ratio (SNR) |
62 dB(A) @ 16 dB gain |
|
Total harmonic distortion (THD) |
0.02% |
|
Input clock frequency |
1 MHz to 4 MHz (2.4 MHz recommended) |
|
MIC input ESD rating |
1.5 kV HBM |
|
Operating temperature |
-40°C to 85°C |
|
Package |
6-WLCSP (1.24 mm × 0.84 mm) |
Source: onsemi.
Operating Principle and Interface
The signal chain of the FAN3852 is very simple: the analog output of the ECM enters the INPUT pin through an AC coupling capacitor. After conditioning by the internal preamplifier, it drives the oversampling Sigma-Delta ADC, which converts it into a 1-bit PDM data stream. This stream is output directly from the DATA pin to the host's PDM audio interface. The chip uses a standard 5-wire digital interface. In addition to power and ground, only three signal lines are needed for communication: CLOCK, DATA, and SELECT. The SELECT pin is used to select the output edge of the PDM data: when connected to GND, data is output on the falling edge of the clock; when connected to VDD, it is output on the rising edge. This feature makes dual-microphone array design extremely simple-connect the SELECT pins of two FAN3852 devices to high and low levels respectively, connect the clock and DATA lines in parallel, and the host can read both microphone signals simultaneously through a single PDM interface.
Design Considerations
The choice of clock frequency requires special attention. Although the datasheet specifies support for an input clock of 1 to 4 MHz, measurements show that when the frequency is below 2 MHz, the SNR drops by 1 to 2 dB. Production parameters are measured at the standard 2.4 MHz clock, so 2.4 MHz should be preferred for applications with audio quality requirements. In addition, the chip's power supply rejection ratio is outstanding. When a 100 mV, 1 kHz ripple is superimposed on a 3.3 V supply, the increase in output noise floor is less than 1 dB, so no separate power domain is needed for it.
Q&A
Q: What are the advantages of the FAN3852UC16X compared with a solution using a discrete preamplifier plus an external ADC?
A: The core advantages are integration and space. A discrete solution requires a preamplifier, an ADC, an LDO, and multiple passive components, with a PCB area that can reach 10 mm², and it is prone to introducing noise floor. The FAN3852 integrates the three core components into a WLCSP package of about 1 mm². Only one AC coupling capacitor and one decoupling capacitor are needed externally, significantly reducing BOM count and layout difficulty.
Q: Is its ESD protection sufficient for the assembly and usage scenarios of consumer-grade products?
A: The MIC input pin has a 1.5 kV HBM ESD protection rating. For consumer products such as TWS earbuds and voice recorders, no additional ESD protection device is usually needed on the input path. This saves BOM cost and also avoids the effect of the protection device's parasitic capacitance on the microphone signal.
Overall, with its extremely small package size, complete ECM-to-PDM signal chain integration, and operating power as low as 0.85 mW, the FAN3852UC16X provides a cost-effective single-chip solution for space-constrained portable audio capture devices.
Fudong Communication (Shenzhen) Group Co., Ltd., established in 2004, is a specialized global first tier semiconductor agent/distributor.
Fudong Mall is an online e-commerce platform belonging to Fudong Communication (Shenzhen) Group Co., Ltd. Fudong collaborates with global electronic component distributors and Chinese spot inventory suppliers.
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