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ES9219 Datasheet

February 27, 2020

CONFIDENTIAL ADVANCE INFORMATION 1.0.4

ESS TECHNOLOGY, INC. 237 South Hillview Drive, Milpitas, CA 95035, USA Tel (408) 643-8800 • Fax (408) 643-8801

Output Switch

The output signal is selected by an ultra-low THD analog switch that connects either to the HiFi audio headphone amplifier or to an alternate audio

source. A typical alternate source may be voice or another DAC. There are two different ways to use the output switch:

LowFi Mode

The ultra-low THD analog switch may be controlled using Register 32: AMPLIFIER CONFIGURATION. This allows audio to pass from an

alternate source to the output. The digital core remains powered on and ready for a quick transition back to HiFi mode. All supplies must

be enabled.

Low Power Bypass Mode

The ultra-low THD analog switch may be controlled using GPIO2 after RESETb is asserted and the chip is in standby. This allows audio to

pass from an alternate source to the output without the use of the digital core. AVCC_HP and AVCC_CP supplies must be enabled.

This mode is activated when RESETB = pulled down and GPIO2=pulled up.

Analog THD Removal (ATR)

The ESS Sabre DAC’s can be operated in 2 fundamental modes of operation, Voltage Mode and Current Mode.

Voltage mode

The Sabre DAC is connected to a single OPAMP operating in the Differential to Single Ended mode. This mode is cost efficient, however

it exposes the 2nd and 3rd order voltage coefficients of the on die poly-silicon resistors used in the D/A conversion interface. There are 64

poly-silicon unit weight resistors that sum together to make the analog representation of the digital value. Each resistor contributes 1/64th

of the output, and each resistor is exposed to a signal dependent voltage across it. The 2nd and 3rd order terms create 2nd and 3rd order

harmonics from this simplified equation of the resistor.

Rab = Rnom + (Rnom * Vab * Vc22) + (Rnom * Vab * Vc33)

Where:

Rab: Resistance across the resistor terminals

Rnom: The Nominal value of the resistor.

Vab: Voltage across the resistor terminals

Vc2: Squared Voltage coefficient term

Vc3: Cubed Voltage coefficient term

Current mode

In this mode of operation of the Sabre DAC, the output of the DAC is held at a virtual ground, therefore the current going though each of

the has only 2 states, either sourcing our sinking. Even though the resistors still have the 2nd and 3rd order voltage coefficients, there is

only ever 2 voltages applied across the resistor, which means that the 2nd and 3rd order terms end up being a DC offset instead of

harmonic distortion. This is typically done by connecting the Sabre DAC to an I/V convertor stage, then to a Differential to Single Ended

stage, which requires 3 opamps to implement.

The ES9219 Implements analog circuitry that puts the Sabre DAC’s into “Current Mode” by integrating the I/V stage. This allows the Sabre DAC’s

to achieve the best possible linearity.

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