A22H165 STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 36
Technical content
Datasheet sections
- 1 Absolute maximum ratings and operating conditions
- 2 Typical application sche matic
- 3 Electrical characteristics
- 4 Application information
- 4.1 Gain control
- 4.2 Overview of the class-G, 2-level headphone amplifier
- 4.3 External component selection
- 4.3.1 Step-down inductor selection (L1)
- 4.3.2 Step-down output capacitor selection (C t)
- 4.3.3 Full capacitive inverter capacitors selection (C12 and CSS)
- 4.3.4 Power supply decoupling capacitor selection (Cs)
- 4.3.5 Input coupling capacitor selection (C in)
- 4.3.6 Low-pass output filter (R out and Cout) and IEC 61000-4-2 ESD
- 4.3.7 Integrated input low-pass filter
- 4.4 Single-ended input configuration
- 4.4.1 Layout recommendations for single-ended operation
- 4.5 Startup phase
- 4.5.1 Auto zero technology
- 4.5.2 Input impedance
- 4.6 Layout recommendations
- 4.6.1 Common-mode sense layout
- 5 Package information
- 6 Revision history
Features
Power supply range: 2.3 V to 4.8 V 0.6 mA/channel quiescent current 2.1 mA current consumption with 100 µW/channel (10 dB crest factor) 0.006% typical THD+N at 1 kHz 100 dB typical PSRR at 217 Hz 100 dB of SNR A-weighted at G = 0 dB Zero "pop and click" Gain settings: 0 dB and 6 dB Integrated high efficiency step-down converter Low standby current: 5 µA max Output-coupling capacitors removed Thermal shutdown Flip-chip package: 1.65 mm x 1.65 mm, 400 µm pitch, 16 bumps
Applications
Cellular / smart phones Portable media player Wearable Fitness and healthcare
Description
The A22H165 is a class-G stereo headphone driver dedicated to high-performance audio, high power efficiency and space-constrained applications. It is based on the core technology of a low power dissipation amplifier combined with a high efficiency step-down DC-DC converter for supplying this amplifier. When powered by a battery, the internal step down DC-DC converter generates the appropriate voltage to the amplifier depending on the amplitude of the audio signal to supply the headsets. It achieves a total 2.1 mA current consumption at 100 µW output power (10 dB crest factor). THD+N is 0.02 % maximum at 1 kHz and PSRR is 100 dB at 217 Hz, which ensures a high audio quality of the device in a wide range of environments. The traditionally bulky output coupling capacitors can be removed. A dedicated common-mode sense pin removes parasitic ground noise. The A22H165 is designed to be used with an output serial resistor. It ensures unconditional stability over a wide range of capacitive loads. The A22H165 is packaged in a tiny 16-bump flip-chip package with a pitch of 400 µm. TOP VIEW AVDD SWINL- CMS EN AGND HPVDD VOUTL VOUTR INL+ INR+ PVSS GAININR- 4321 A B C D A22H165 - Flip-chip Pinout (top view) Balls are undemeath Table 1. Device summary
1 Absolute maximum ratings and operating conditions
Table 2. Absolute maximum ratings VCC Supply voltage (1) during 1 ms.
- All voltage values are measured with respect to the ground pin.
- Thermal shutdown is activated when maximum junction temperature is reached.
- The device is protected from over temperature by a thermal shutdown mechanism, active at 150° C.
- Exceeding the power derating curves for long periods may provoke abnormal operation.
- Human body model: a 100 pF capacitor is charged to the specified voltage, then discharged through a
while the other pins are floating.
- Machine model: a 200 pF capacitor is charged to the specified voltage, then discharged directly between
connected pin combinations while the other pins are floating.
- The measurement is performed on an evaluati on board, with ESD protection EMIF02-AV01F3.
Table 3. Operating conditions
2 Typical application schematic
Figure 1. Typical application schematic for the A22H165 Table 4. A22H165 pin description
Table 5. A22H165 component description recommended to minimize C/V when VCC =4 . 8V .
6.3 V rating voltage is recommended to minimize C/V when
filter with a -3 dB cut-off frequency Fc. mandatory for operation of the A22H165. resistor is mandatory for operation of the A22H165. L1 3.3 µH Inductor for internal DC-DC step-down converter. References of inductors: refer to Section 4.3.1 for more information.
- Refer to Section 4.3 for a complete description of each component.
3 Electrical characteristics
GAIN = 0 dB, RL= 32 + 15 , Tamb = 25° C, unless otherwise specified. Table 6. Electrical characteristics of the amplifier
- Guaranteed by design and parameter correlation.
Table 6. Electrical characteristics of the amplifier (continued)
4 Application information
4.1 Gain control
Note: See Table 6: Electrical characteristics of the amplifier for VIH and VIL levels.
4.2 Overview of the class-G, 2-level headphone amplifier
device, the power supply uses two levels: ±1.2 V and ±1.9 V.
0 V, thus eliminating the classical bulky DC blocking output capacitors (typically more than
Figure 64. A22H165 architecture
4.3 External co mponent selection
component is described in the following sections.
4.3.1 Step-down inductor selection (L1)
Table 7 shows the part number that should be used according to the inductor value.
4.3.2 Step-down output capacitor selection (C t)
For the internal DC-DC step-down converter, the A22H165 needs one output capacitor. avoid oscillation of the converter. Therefore the following constraints must be observed. resistance that have a negative impact on the audio performance. Table 7. Recommended inductor Table 8. Recommended capacitors
4.3.3 Full capacitive inverter ca pacitors selection (C12 and CSS)
Two capacitors (C12 and Css) are needed for this internal DC-DC inverter. The three criteria for selecting these capacitors are the range value of the capacitor including self tolerance, DC variation and the minimum ESR to minimize power losses. Typical capacitor value: 2.2 µF +/-20 % Voltage across these capacitors: from 1.1 V to 2 V Minimum capacitor value: 1 µF Again, a ceramic capacitor in a 0603 or 0402-type package is also recommended because of their close placement to the A22H165, which makes it easier to minimize parasitic inductance and resistance that have a negative impact on the audio performance.
4.3.4 Power supply decoupl ing capacitor selection (Cs)
A 2.2 µF decoupling capacitor with low ESR is recommended for positive power supply decoupling. Packages such as the 0402 or 0603 are also recommended because of their close placement to the A22H165, which makes it easier to minimize parasitic inductance. It is advised to choose a X5R dielectric for capacitor tolerance, and a 10 V DC rating voltage for 4.8 V operations (or a 6.3 V DC rating voltage for 3.6 V operations), to take into consideration the C/V variation of this type of ceramic capacitor. An important parameter is the rated voltage of the capacitor. A 2.2 µF/6.3 V capacitor used at 4.8 V DC typically loses about 40 % of its value. In fact, with a 4.8 V power supply voltage, the decoupling value is about 1.3 µF instead of 2.2 µF. Because the decoupling capacitor influences the THD+N in the medium-to-high frequency region, this capacitor variation becomes decisive. In addition, less decoupling means higher overshoots, which can be problematic if they reach the power supply’s AMR value (5.5 V). This is why, for a 2.2 µF value, we recommend a 2.2 µF/10 V, a 4.7 µF/6.3 V or a ceramic capacitor with a low DC bias variation rated at 6.3 V.
4.3.5 Input coupling capacitor selection (C in)
Cin input coupling capacitors are mandatory for the A22H165’s operation. They block any DC component coming from the audio signal source. Cin with Rin form a first-order high-pass filter and the -3 dB cut-off frequency is: Rin is the single-ended input impedance that can be approximated at about Rindiff/2. Rin also depends on the gain setting. Figure 10 provides the differential input impedance vs. gain. One can also see that Rindiff is minimum for the maximum gain setting (that is, 6 dB). Therefore, in most cases, Rin should be set to 6 dB to calculate the minimum input capacitor Cin. Example: In this case and for a -3 dB cut-off frequency of 20 Hz, C in =0 . 6 4µF. The closest normalized value is 0.68 µF but a 1 µF capacitor is more suitable to take into consideration the capacitor tolerance +/-20 %. If the aim is to have the 20 Hz at -1 dB, the capacitor has to be multiplied by 1.96. As such, FC 3dB– 1
4.3.6 Low-pass output filter (R out and Cout) and IEC 61000-4-2 ESD
the volume range and output capacitance range vs. load. a classic headphone (16 , 32 , 60 ) and the line-in of any hi-fi system or sound card. (a) reference EMIF02-AV01F3. A22H165 as shown in Figure 67. Figure 67. Typical application schematic with IEC 61000-4-2 ESD protection a. Copyright STMicroelectronics.
4.3.7 Integrated input low-pass filter
4.4 Single-ended input configuration
same value to keep the same PSRR performance as in a differential input configuration. done on the ground of the audio source and not on the ground of the A22H165 itself. Figure 68. Single-ended input configuration1
Figure 69. Single-ended input configuration 2 With reference to Figure 69, note that the absolute phase in the audio band is 180°.
4.4.1 Layout recommendations for single-ended operation
The connection location of each input that has to be set to ground is extremely important.
Figure 70. Incorrect ground connection for single-ended option voltage can be expressed by the following simplified equation from an AC point of view. audio source device (no parasitic AC voltage), it is not necessarily the case for Vgndnoise.
the audio signal and grounded with the ground of the audio source. Figure 71. Correct ground connection for single-ended option
4.5 Startup phase
The A22H165 uses different techniques to reduce the DC current consumption and offer a pop-and-click performance close to none.
4.5.1 Auto zero technology
During the startup phase, the differential output voltage is sensed and adjusted to 0 V (+/-500 V) to avoid any pop noise when the amplifier becomes operational. This also helps to minimize extra current consumption due to the load (Icc-extra = VoutDC / Rload).
4.5.2 Input impedance
The A22H165 requires input coupling capacitors. The usual lowest frequency used for the headphone is close to 20 Hz. This frequency means a constant time for a first-order high- pass filter of approximately 1 / (2 x Pi x 20) = 8 ms. To achieve 95 % of the capacitor’s charge, it is necessary to wait 3 x 8 ms = 24 ms, which is out of range for a device with a fast startup time. Because of the mismatching of all input capacitors and input resistors, if it is decided to start the A22H165 at a time of 8 ms, a voltage difference at the inputs (multiplied by the gain) can create a voltage step on the output and consequently a pop noise. To avoid this issue during the starting phase, the A22H165 accelerates the charging of the input capacitors by reducing the input impedance to 2 k. In such a case, for a 1 F capacitor the 95 % charge is reached in 6 ms. As the startup time of A22H165 is 12 ms, there remains sufficient time to fully charge the input capacitors and as such eliminate any pop noise.
4.6 Layout recommendations
Particular attention must be given to the correct layout of the PCB traces and wires between the amplifier, load and power supply (in most cases, the battery of the cellular phone). The power and ground traces are critical since they must provide adequate energy and grounding for all circuits. Good practice is to use short and wide PCB traces to minimize voltage drops and parasitic inductance. A track with a width of at least 200 m for a copper thickness of 18 m is recommended for bringing energy to the amplifier from the battery. Proper grounding guidelines help improve audio performances, minimize crosstalk between channels, and prevent switching noise from coupling into the audio signal. It is also recommended to use a large-area and multi-via ground plane to minimize parasitic impedance. A multi-layer PCB board allows double or multiple ground planes to be implemented. Most of the time, the top and bottom layers are used as ground planes and provide shielding for tracks routed on the intermediate layers. In addition, to minimize parasitic impedance over the entire surface, a multi-via technique that connects the bottom and top layer ground planes together in many locations is often used. The copper traces that connect the output pins to the load and supply pins should be as wide as possible to minimize the trace resistances.
4.6.1 Common-mode sense layout
can create parasitic noise in the headphone and/or line out. removed from the A22H165 outputs. Figure 72. Common-mode sense layout example
5 Package information
specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Figure 73. A22H165 footprint recommendation Figure 74. Pinout
6 Revision history
Table 9. Document revision history 06-Mar-2014 1 Initial release.