SAMHOP Microelectronics Corp.
3W STEREO AUDIO POWER AMPLIFIER WITH ADVANCED DC VOLUME CONTROL
HP/LINE OPERATION
The HP/LINE input controls the internal input multiplexer (MUX). Refer to the block diagram in Figure 3. This
allows the device to switch between two separate stereo inputs to the amplifier. For design flexibility, the
HP/LINE control is independent of the output mode, SE or BTL, which is cotrolled by the aforementioned
SE/BTL pin. To allow the amplifier to switch from the LINE inputs to the HP inputs when the output switches
from BTL mode to SE mode, simply connect the SE/BTL control input to the HP/LINE input.
When this input is logic high, the RHPIN and LHPIN inputs are selected. When this terminal is logic low, the
RLINEIN and LLINEIN inputs are selected. This operation is also detailed in Table 3 and the trip levels for a
logic low (VIL) or logic high (VIH) can be found in the recommended operating conditions table.
Table 3. HP/LINE, SE/BTL, and Shudown Functions
INPUTS (1)
SE/BTL
X
AMPLIFIER STATE
INPUT OUTPUT
HP/LINE
X
SHUTDOWN
Low
X
MUTE
BTL
SE
Low
Low
High
LINE
LINE
HP
Low
High
High
High
High
Low
High
BTL
SE
High
High
HP
(1) Inputs should never be left unconnected
SHUTDOWN MODES
The SM7511 employs a shutdown mode of operation designed to reduce supply current (IDD) to the absolute
minimum level during periods of nonuse for battery-power conservation. The SHUTDOWN input terminal should
be held high during normal operation when the amplifier is in use. Pulling SHUTDOWN low causes the outputs
to mute and the amplifier to enter a low-current state, IDD= 20μA. SHUTDOWN should never be left
unconnected because amplifier operation would be unpredictable.
FADE OPERATION
For design flexibility, a fade mode is provided to slowly ramp up the amplifier gain when coming out of
shutdown mode and conversely ramp the gain down when going into shutdown. This mode provides a smooth
transition between the active and shutdown states and virtually eliminates any pops or clicks on the outputs.
When the FADE input is a logic low, the device is placed into fade-on mode. A logic high on this pin places the
amplifier in the fade-off mode. The voltage trip levels for a logic low (VIL) or logic high (VIH) can be found in the
recommended operating conditions table.
When a logic low is applied to the FADE pin and a logic low is then applied on the SHUTDOWN pin, the
channel gain steps down from gain step to gain step at a rate of two clock cycles per step. With a nominal
internal clock frequency of 58Hz, this equates to 34 ms per step. The gain steps down until the lowest gain step
is reached. The time it takes to reach this step depends on the gain setting prior to placing the device in
shutdown. For example, if the amplifier is in the highest gain mode of 20 dB, the time it takes to ramp down the
channel gain is 1.05 seconds. This number is calculated by taking the number of steps to reach the lowest gain
from the highest gain, or 31 steps, and multiplying by the time per step, or 34 ms.
V.1.3 Revised April 02,2007
Page 11
SAMHOP [ SAMHOP MICROELECTRONICS CORP. ]
