Datasheet
Maxim Integrated
│
144
MAX98090 Ultra-Low Power Stereo Audio Codec
www.maximintegrated.com
Range 1 (V
HP_OUT
< 10% of V
HPVDD
): When the out-
put signal level is less than 10% of HPVDD, the output
signal swing is low and the power consumption for driving
the headphone load is small relative to the charge pump
quiescent consumption and switching losses. Therefore,
to minimize switching losses, the charge-pump frequency
is reduced to its lowest rate (~82kHz) and the bipolar out-
put supply rails are set to half of HPVDD or ±V
HPVDD
/2
(Figure 40, Range 1).
Range 2 (10% of V
HPVDD
≤ V
HP_OUT
< 25% of
V
HPVDD
): When the output signal level is between 10%
and 25% of HPVDD, the output signal swing is still less
than half of HPVDD. However, the load power consumption
requirements are now much higher than the charge-pump
quiescent consumption and switching losses. To meet the
increased load power requirements, the charge-pump
switching frequency increases (~660kHz) while the bipolar
output supply rails remain at half of HPVDD or ±V
HPVDD
/2
(Figure 40, Range 2).
Range 3 (25% of V
HPVDD
≤ V
HP_OUT
): When the
output signal level exceeds 25% of HPVDD, the output
signal swing is much wider. As a result, the charge pump
now generates bipolar full HPVDD output supply rails
(±V
HPVDD
). The switching frequency in this range is
slightly lower (~500kHz). However, the increased voltage
differential allows the headphone output driver to reach
its maximum voltage swing and load driving capability
(Figure 40, Range 3).
Figure 40. Class H Amplifier Charge Pump Operating Ranges
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
V
HPVDD
V
HPVDD
2
-V
HPVDD
-V
HPVDD
2
GND
POSITIVE TERMINAL (C1P)
NEGATIVE TERMINAL (C1N)
POSITIVE TERMINAL (C1P)
NEGATIVE TERMINAL (C1N)
POSITIVE TERMINAL (C1P)
NEGATIVE TERMINAL (C1N)
OPERATING RANGE 1
V
HP_OUT
< 10% V
HPVDD
OPERATING RANGE 2
10% V
HPVDD
≤ V
HP_OUT
< 25% V
HPVDD
OPERATING RANGE 3
25% V
HPVDD
≤ V
HP_OUT