SB3231-E1-T Datasheet SB3231-E1-T, SB3231-E1 | P10-P12

RHYTHM SB3231

www.onsemi.com

Memory Select Switches

One or two, two−pole Memory Select (MS) switches can

be used with Rhythm SB3231. This enables user

tremendous flexibility in switching between configurations.

Up to four memories can be configured and selected by the

MS switches on Rhythm SB3231. Memory A must always

be valid. The MS switches are either momentary or static

and are fully configurable through IDS in the IDS setting

tab.

The behavior of the MS switches is controlled by two

main parameters in IDS:

MSSmode: this mode determines whether a

connected switch is momentary or static.

Donly: this parameter determines whether the MS2

switch is dedicated to the last memory position

There are four basic MS switch modes of operation as

shown in Table 4 below.

Table 4. MS SWITCH MODES

MS Switch Mode MS1 Switch MS2 Switch

Max # of Valid

Memories

Donly MSSMode Use

Mode 1 Momentary None 4 Off Momentary Simplest configuration

Mode 2 Momentary Static 4 On Momentary Jump to last memory

Mode 3 Static Static 4 Off Static Binary selection of memory

Mode 4 Static Static 3 On Static Jump to last memory

The flexibility of the MS switches is further increased by

allowing the MS switches to be wired to GND or VBAT,

corresponding to an active low or active high logic level on

the MS pins. This option is configured with the

MSPullUpDown/MS2PullUpDown setting in the IDS

settings tab as shown in Table 5 below.

Table 5. MS SWITCH LOGIC LEVELS VS. IDS PULLUPDOWN SETTINGS

“PullUpDown” Setting in IDS MS Switch State MS Input Logic Level Switch Connection

Pulldown CLOSED HI To VBAT

Pulldown OPEN LOW To VBAT

Pullup CLOSED LOW To GND

Pullup OPEN HI To GND

In the following mode descriptions, it is assumed that the

PullUpDown setting has been properly configured for the

MS switch wiring so that a CLOSED switch state is at the

correct input logic level.

Mode 1: Momentary Switch on MS1

This mode uses a single momentary switch on MS1 input

to change memories. Using this mode causes the part to start

in memory A, and whenever the button is pressed, the next

valid memory is loaded. When the user is in the last valid

memory, a button press causes memory A to be loaded.

Thus, the possible selection sequences are:

• If 4 valid memories: ABCDABCDA…

• If 3 valid memories: ABCABCA…

• If 2 valid memories: ABABA…

• If 1 valid memory: AAA…

Mode 2: Momentary Switch on MS1, Static Switch on

MS2 (D−only, Jump to Last Memory)

This mode uses a static switch on MS2 and a momentary

switch on MS1 to change memories. It can be used to support

the Automatic Telecoil feature, see section Automatic

Telecoil.

If the static switch on MS2 is OPEN, the part starts in

memory A and is controlled by the momentary switch on

MS1 as described in section Momentary Switch on MS1,

with the exception that memory D is not used. If the static

switch on MS2 is set to CLOSED, the part automatically

jumps to memory D (occurs on startup or during normal

operation). In this setup, the state of the momentary switch

on MS1 is ignored. When MS2 is set to OPEN, the part loads

in the memory that was active prior to jumping to memory

The possible memory selection sequences are:

If MS2 = OPEN and there are four valid memories, MS1

selects: ABCABCA…

If MS2 = OPEN and there are three valid memories, MS1

selects: ABABA…

If MS2 = OPEN and there is one valid memory: A

If MS2 = CLOSED: D

Mode 3: Static Switch on MS1 and MS2

This mode uses two static switches to change memories.

In this mode, it is possible to jump from any memory to any

other memory by changing the state of both switches. If the

two switches are changed one after the other, the part

RHYTHM SB3231

www.onsemi.com

transitions to an intermediate memory before reaching the

final memory. The part starts in whatever memory the

switches are selecting. If a memory is invalid, the part

defaults to memory A.

Table 6. STATIC SWITCH TRUTH TABLE:

D−ONLY DISABLED

State (MS1/MS2) Selected Memory

OPEN OPEN Memory A

CLOSED OPEN Memory B

OPEN CLOSED Memory C

CLOSED CLOSED Memory D

Mode 4: Static Switch on MS1, Static Switch on MS2

(D−Only, Jump to Last Memory)

This mode uses two static switches to change memories.

Similar to the behaviour described in the Static Switch on

MS1 and MS2 section, this mode will switch to memory D

if the static switch on MS2 is HIGH (the state of the switch

on MS1 is ignored). The mode, however, supports

a maximum of three memories (even if four valid memories

are programmed). This mode can be used to support the

Automatic Telecoil feature (see the Automatic Telecoil

section).

In this mode, it is possible to jump from any memory to

any other memory by changing the state of both switches. If

the two switches are changed one after the other, the part

transitions to an intermediate memory before reaching the

final memory.

The part starts in whatever memory the switches are

selecting. If a memory is invalid, the part defaults to

memory A.

Table 7. STATIC SWITCH TRUTH TABLE:

D−ONLY ENABLED; (EXAMPLE WITH THREE VALID

MEMORIES)

State (MS1/MS2) Selected Memory

OPEN OPEN Memory A

CLOSED OPEN Memory B

X CLOSED Memory D

Rocker Switch Support

The device supports connection of a rocker switch to the

digital volume control interface that can perform volume

control (VC) adjustments and/or memory selection (MS).

There are three modes of operation:

• Digital Volume Control Mode

• Momentary Memory Select Mode

• Mixed Mode (VC and MS)

In Digital VC mode, the rocker switch provides the digital

volume control functionality described in this section.

In Momentary Memory Select mode, the rocker switch

allows cycling through the memory profiles in both

directions. An “up” switch closure indicates a program

advance to the next higher numbered memory and “down”

switch closures indicates a program retreat to the next lower

numbered memory. In this mode, volume control is only

available through software control.

In Mixed Mode, operation of the switch as a volume

control or memory select is governed by the time duration

of the switch closure: either short or long. The

discrimination of short and long pulses is set by

a programmable, time−threshold value, from 1 s to 5 s in 1 s

increments. An additional programmable parameter

determines whether the short pulses refer to volume−control

operation or memory−select operation.

If long pulses control memory select operation, the

memory change is initiated once the switch is held for the

long pulse period without requiring the switch to be

released. In Digital VC mode or Momentary Memory Select

mode, the action takes place after the switch is released.

AGC−O

The AGC−O module is an output limiting circuit with

a fixed compression ratio of ∞ : 1. The limiting level is

programmable as a level measured in dB from full scale. The

maximum output of the device is 0 dBFS.

The AGC−O module has its own level detector, with

programmable attack and release time constants.

Graphic Equalizer

Rhythm SB3231 has a 8−band graphic equalizer. Each

band provides up to 31 dB of gain adjustment in 1 dB

increments.

Biquadratic Filters

Additional frequency shaping can be achieved by

configuring generic biquad filters. The transfer function for

each of the biquad filters is as follows:

H(z) +

b0 ) b1 z

) b2 z

1 ) a1 z

) a2 z

NOTE: The a0 coefficient is hard−wired to always be

‘1’. The coefficients are each 16 bits in length

and formatted as one sign bit, one integer bit and

14 fractional bits. This maps onto a decimal

range of −2.0 to 2.0 before quantization (−32767

to 32767 after quantization).

Thus, before quantization, the floating−point coefficients

must be in the range −2.0 ≤ x < 2.0 and quantized with the

function:

round(x 2

)

After designing a filter, the quantized coefficients can be

entered into the PreBiquads or PostBiquads tab in the

Interactive Data Sheet. The coefficients b0, b1, b2, a1, and

a2 are as defined in the transfer function above. The

parameters meta0 and meta1 do not have any effect on the

signal processing, but can be used to store additional

information related to the associated biquad.

RHYTHM SB3231

www.onsemi.com

The underlying code in the product components

automatically checks all of the filters in the system for

stability (i.e., the poles have to be within the unit circle)

before updating the graphs on the screen or programming

the coefficients into the hybrid. If the Interactive Data Sheet

receives an exception from the underlying stability checking

code, it automatically disables the biquad being modified

and displays a warning message. When the filter is made

stable again, it can be re−enabled.

Also note that in some configurations, some of these

filters may be used by the product component for

microphone/telecoil compensation, low−frequency EQ, etc.

If this is the case, the coefficients entered by the user into

IDS are ignored and the filter designed by the software is

programmed instead. For more information on filter design

refer to the Biquad Filters In PARAGON

Digital Hybrid

information note.

Tinnitus Treatment Noise

The Tinnitus Treatment noise is generated using white

noise generator hardware and shaping the generated noise

using four 2

order biquadratic filters. The filter parameters

are the same coefficients as those presented in the

Biquadratic Filters section.

The Tinnitus Treatment noise can be added into the signal

path at two possible locations: before the VC (before the

AGC−O, but compensated for the Wideband Gain) or after

the VC (between the last generic biquad and the Cross

Fader).

If the noise is injected before the VC and the audio path

is also enabled, the device can be set up to either have both

the audio path and noise adjust via the VC, or to have only

the noise adjust via the VC (see Table 8). If the noise in

injected after the VC, it is not affected by VC changes.

Table 8. NOISE INSERTION MODES

Noise Insertion Modes VC Controls Noise Injected

Off Audio Off

Pre VC Audio + Noise Pre VC

Post VC Audio Post VC

Noise only Pre VC Noise Pre VC

Noise only Post VC − Post VC

Pre VC with Noise Noise Pre VC

8.14 EVOKE Lite Acoustic Indicators

Ten Acoustic Indicators are available for indicating

events. Each indicator is fixed to a particular event. Any

event can have its assigned indicator enabled or disabled

although not always independently. Individual

enable/disable control is provided for the following event or

group of events:

• Power on reset (POR)

• Four memory selects

• Volume Up and Volume Down

• Volume Max and Volume Min

• Low Battery

Each Acoustic Indicator is made up of up to four faded

tones. A faded tone exhibits a nominal 32 ms fade−in and

fade−out transition time. The duration of an Acoustic

Indicator is configurable, with a maximum value of 6.35

seconds.

EVOKE Lite Acoustic Indicators can be programmed as

output referred or input referred (prior to the filter bank).

Power Management

Rhythm SB3231 has three user−selectable power

management schemes to ensure the hearing aid turns off

gracefully at the end of battery life. Shallow reset, Deep reset

and Advanced Reset mode. It also contains a programmable

power on reset delay function.

Power On Reset Delay

The programmable POR delay controls the amount of

time between power being connected to the hybrid and the

audio output being enabled. This gives the user time to

properly insert the hearing aid before the audio starts,

avoiding the temporary feedback that can occur while the

device is being inserted. During the delay period,

momentary button presses are ignored.

Power Management Functionality

As the voltage on the hearing aid battery decreases, an

audible warning is given to the user indicating the battery

life is low. In addition to this audible warning, the hearing

aid takes other steps to ensure proper operation given the

weak supply. The exact hearing aid behaviour in low supply

conditions depends on the selected POR mode. The hearing

aid has three POR modes:

• Shallow Reset Mode

• Deep Reset Mode

• Advanced Mode

Shallow Reset Mode

In Shallow Reset mode, the hearing aid will operate

normally when the battery is above 0.95 V. Once the supply

voltage drops below 0.95 V the audio will be muted and

remain in that state until the supply voltage rises above

1.1 V. Once the supply voltage drops below the control logic

ramp down voltage, the device will undergo a hardware

reset. At this point, the device will remain off until the supply

voltage returns to 1.1 V. When the supply voltage is below

the control logic voltage, but above 0.6 V and rises above the

1.1 V turn on threshold, the device will activate its output

and operate from the memory that was active prior to reset.

If the supply voltage drops below 0.6 V, and rises above the

1.1 V turn on threshold, the device will reinitialize, activate

its output and operate from memory A.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18

SB3231-E1-T

Mfr. #:

Buy SB3231-E1-T

Manufacturer:

ON Semiconductor

Description:

Audio DSPs PRECONFIG DSP: RHYTH

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

SB3231-E1-T

SB3231-E1-T

Products related to this Datasheet