APA2057A
Application Information (Cont.)
drive.
Charge Pump Output Capacitor
·
·
Both amplifier and headphone “ON” mode: Pull low
the AMP_EN and pull high the HP_EN control pins,
then turn on both speaker drivers and headphone
drivers
The output capacitor (CCPO)’s value affects the power
ripple directly at CVSS(VSS). Increasing the value of output
capacitor reduces the power ripple. The ESR of output
capacitor affects the load transient of CVSS(VSS). Lower
ESR and greater than 1mf ceramic capacitor (X7R type
is recommended) is recommendation.
Both amplifier and headphone “OFF” mode: Pull
high the AMP_EN and pull low the HP_EN control
pins, then turn off both speaker drivers and head-
phone drivers
Charge Pump Bypass Capacitor
The bypass capacitor (CCPB) relates with the charge pump
switching transient. The capacitor’s value is same as
flying capacitor (1mf). Place it close to the CVDD and PGND.
If the AMP_EN and HP_EN are connected together, then
this pin will be connected to headphone jack’s control
pin (Figure 3), the APA2057A is switchable between “Am-
plifier mode (Headphone mute), or Headphone mode
(Amplifier mute).
Headphone Detection Input
HP_R
Control pin
Ring
1KW
Gain Setting
The gain for speaker drivers can be adjustable by apply-
ing DC voltage to SET pin. The APA2057A control con-
sists 19 step gain settings from 2.0V~ 4.2V, and the gain
is from -7dB to 16dB. Each gain step corresponds to a
specific input voltage range, as shown in “Gain Setting
Table”. To minimize the effect of noise on the gain setting
control, which can affect the selected gain level, hyster-
esis and clock delay are implemented. For the highest
accuracy, the voltage shown in the “recommended volt-
age” column of the table is used to select a desired gain.
This recommended voltage is exactly halfway between
the two nearest transitions. The amount of hysteresis
corresponds to half of the step width, as shown in Fig-
ure 4. Apply 0V to SET pin will place the APA2057A into
shutdown mode, and when SD =5V, it allows the speaker
HPD_Switch
HP_EN
HP_L
1KW
Sleeve
Tip
Headphone Detection
Headphone Jack with swich
Figure 3 HPD configurations
The HP_EN will detect the voltage. If the voltage is
less than 0.8V, the headphone amplifiers will be disabled;
if greater than 2V, then the headphone amplifier will be
enabled.
In Figure 3, phone-jack with the control pin is used and
connected to HP_EN input from control pin. When a
headphone plug is inserted, the HP_EN will pull high
internally which enables headphone amplifiers; with-
out headphone plug, the HP_EN is pulled to GND.
driver at a fixed gain (AV=10.5dB).
20
10
0
Forward
Operation Mode
Backward
The APA2057A amplifier has two pairs of independent
amplifier. One for stereo speaker is BTL structure, and
the other for headphone is cap-less structure. Each pair
has independent input pin; INR_A and INA_L are for ste-
reo speaker drivers, and INR_H and INL_H are for
stereo headphone drivers.
-10
-20
-30
-40
-50
-60
-70
·
Amplifier mode operation: Pull low the AMP_EN
control pin can enable the stereo speaker driver.
Headphone mode operation: Pull high the HP_EN
control pin can enable the cap-less headphone
3.
0
0.0
1.0
2.0
4.0
5.0
·
DC Volume (V)
Figure 4: APA2057A Gain setting vs. SET pin Voltage
Copyright ã ANPEC Electronics Corp.
22
www.anpec.com.tw
Rev. A.1 - Aug., 2007
ANPEC [ ANPEC ELECTRONICS COROPRATION ]
