Rainbow Electronics MAX5406 - Manual (Page 15)

MAX5406
Audio Processor with Pushbutton Interface
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Up/Down Interface
The MAX5406 features independent control inputs for
volume, balance, ambience, and tone control. All con-
trol inputs are internally debounced for use with
momentary contact SPST switches. All switch inputs
are pulled up to V
LOGIC through 50k
Ω resistors. The
wiper setting advances once per button press held for
up to 1s (see Figures 2a and 2b). Maxim’s SmartWiper
control circuitry allows the wiper to advance at a rate of
4Hz when an input is held low from 1s up to 4s, and at
a rate of 16Hz if the contact is maintained for greater
than 4s without the need of a µP (see Figure 3 and
Table 1). The MAX5406 ignores multiple buttons being
pressed. A µP can also be used to control the
MAX5406.
Volume Control
The MAX5406 implements dual logarithmic potentiome-
ters for volume control that change the sound level by
2dB per button push (see Table 2).
In volume-control mode, the MAX5406’s wipers move
up and down together (see Figure 4). The balance is
unaffected (see the Balance Control section). Left and
right balance settings are maintained when adjusting
the volume.
Balance Control
In balance-control mode, the MAX5406 uses dual
potentiometers to control balance for the left and right
channels. Pressing BALR increases the right channel
wiper by 1dB and decreases the left channel by 1dB.
This causes the right channel to sound louder than the
left channel by 2dB. The overall volume remains con-
stant when adjusting the balance (Figure 5).
Volume and Balance Interaction
Volume and balance operation is simple. However,
there are some interactions that occur at the extreme
wiper positions. These interactions are described in this
section of the data sheet.
When the volume setting is at the maximum level, the
first command to move the balance toward the left chan-
nel forces the right channel to decrease by 1dB.
Subsequent pressing of BALL causes the right channel
to decrease by 2dB. At this position, shown in the right
column of Figure 6a, the left-channel volume is maxi-
mum, but the actual separation between L and R is 3dB.
At this position, pressing VOLDN restores the actual
balance setting only after VOLDN is pressed at least
half as many times as BALL was (previously) pressed
(shown in the middle and right column of Figure 6b) to
increase the right-channel balance.
The volume and balance interaction is similar when vol-
ume setting is at the minimum level.
Tone Control
The MAX5406 implements a linear potentiometer to
control the bass and treble over a range of ±10dB
using the recommended component values.
Note that the actual response achieved is determined
by the values of both external and internal components
and the design equations are somewhat interactive.
Use the values shown in the Electrical Characteristics
as a good starting point for choosing component val-
ues. These components yield shelf turnovers at 100Hz
(bass) and 10kHz (treble) with a total ±10dB of boost at
100Hz and 10kHz. The shoulder or flat portion of the
response is centered on 1kHz.
The circuit in Figure 7 shows the internal structure of
the tone-control system should modification to the
CONTACT
DURATION
WIPER ACTION
t < t LPW No motion (debouncing) (Figures 2a and 2b)
t LPW
≤ t ≤ 1s
Wiper changes position once (Figures 2a
and 2b)
1s ≤ t < 4s
Wiper changes position at a rate of 4Hz
(Figure 3)
t ≥4s
Wiper changes position at a rate of 16Hz
(Figure 3)
Table 1. Wiper Action vs. Pushbutton
Contact Duration
POSITION ATTENUATION (dB)
0 0
1 2
2 4
….. …..
10 ( Power-on state) 20
….. …..
30 60
31 62
32 (Mute) > 90
Table 2. Attenuator Position For Volume
Potentiometers