MAX98400 Audio Power Class D Amplifier

Table of Contents

MAX98400 + CH224K pocket audio power Class D Amplifier with volume adjustment, turning switch, power by PD charger. The MAX98400A/MAX98400B Class D amplifiers offer high-performance and thermally efficient amplifier solutions. The MAX98400A provides 2x20W into 8Ω loads or 1x40W into a 4Ω load, while the MAX98400B delivers 2x12W into 8Ω loads.

An integrated limiting circuit prevents output clipping distortion and protects speakers from transient voltages. A thermal-foldback feature can reduce output power at high temperatures, with traditional thermal protection and overcurrent protection also included. Operating from a single 8V to 28V supply, the ICs offer a high 67dB PSRR and up to 90% efficiency from a 12V supply. Filterless modulation allows the ICs to meet EMI limits with minimal additional components.

Max98400 Audio Power Class D Amplifier-Amplifier

Both devices feature digitally controlled gain settings and click-and-pop reduction circuitry for noise reduction during shutdown.

A small D-class amplifier, very compact with dimensions of only 80mm*50mm, but can output 22W@8Ω*2, solving the problem of not being able to fit other amplifiers into pockets.

Hardware section No major issues, very simple, directly copied from the datasheet, but there is a pitfall, the SHDN pin must be powered separately, do not connect it to VS, otherwise it won’t work. The auxiliary power supply section because I have multiple 7805 and 1117-3.3, and also need to add an LED (actually didn’t want to buy a voltage regulator), so I just did it casually. If done properly, the official circuit below will work and it’s cheaper.

Schematic MAX98400 + CH224K pocket audio power Class D Amplifier

Schematic Max98400 Audio Power Class D Amplifier — Schematic

Gain selection as shown in the table

G1	G2	GAIN SETTING (dB)
GND	GND	9
Unconnected	GND	13
vs	GND	16.7
GND	Unconnected	20.1
Unconnected	Unconnected	23.3
Vs	Unconnected	26.4
GND	vs	29.8
Unconnected	vs	32.9
vs	vs	Reserved

About IC CH224K
CH224 can act as Type-C UFP and support multiple fast charging protocols such as PD on Type-C and Type-A interfaces. It supports E-Mark simulation and the maximum supported power is 100W. The request voltage can be adjusted in real time.

Power for this module can be 12V power supply or 40W PD charger, or 65W

BOM MAX98400 + CH224K audio power Class D Amplifier

Parts	Value	Description	Quantity
Resistors
R7,R1,R2,R3	100K	R0603 – SMD resistor	4
R5	10k	R0603 – SMD resistor	1
R6	1k	R0603 – SMD resistor	1
R8,R9,R10,R11	15	R1206 – SMD resistor	4
R12	RK09712200MY	10kΩ dual Potentiometer	1
R13	82	R0805 – SMD resistor	1
Capacitors
C1,C2,C3,C4	1uF (105)	Film capacitor	4
C6,C14,C24,C15,C5,C7,C8,C13	1uF	C0603 – SMD capacitor	8
C9,C10	680nF	Film capacitor	2
C11,C12,C16,C17,C18,C19 ,C20,C21	150nF	C1206 – SMD capacitor	8
C22	220uF/25V	D8xL11.5mm Aluminum Electrolytic Capacitor	1
Semiconductors
LED1	MHS110UBCT	5mA Side sticker Blue SMD,1.5x3mm LED	1
Q1	AO4411	30V 8A P-Channel SOIC-8 MOSFET	1
U1	MAX98400AETX+T	Stereo, High-Power, Class D Amplifiers	1
U2	CH224K	ESSOP10-EP – USB PD and Other Fast Charging Protocol Sink Controller	1
U3	CJ7805	1.5A Fixed 5V Positive TO-263-2 Voltage Regulators Linear, Low Drop Out (LDO)	1
U5	LD1117-3.3	1A Fixed 3.3V Positive electrode 18V SOT-223 Voltage Regulators – Linear, Low Drop Out (LDO)	1
Miscellaneous
L1,L2,L3,L4	33uH	3A SMD,6.6x7mm Power Inductor	4
DC1	DC-0360-2.5	DC Power Receptacle 2.5mm 6mm Connector	1
SW1	PS22F02L-2B1-21	DPDT Keylock Switch	1
J1	WJ15EDGRC-3.81-4P	1x4P Receptacle-Close Tin Push-Pull, P=3.81mm Pluggable System Terminal Block	1
USB1	TYPE-C16PIN	USB 3.1 3A 16P Female Type-C SMD USB Connector	1
JP1	JUMPER	R0603 – SMD resistor	1
SW4	A6H-4101	4 Positions SPST SMD DIP Switch	1
CN1	PJ-342B-TX-SMT	3.5mm Headphone Jack SMD Audio Connector (Headphone)	1