lm49150tlx National Semiconductor Corporation, lm49150tlx Datasheet - Page 16

• Manufacturer Part Number: lm49150tlx
• Description: Mono Class D Audio Subsystem With Earpiece Driver And Stereo Ground Referenced Headphone Amplifiers
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
I
The LM49150 is controlled through an I
interface that consists of a serial data line (SDA) and a serial
clock (SCL). The clock line is uni-directional. The data line is
bi-directional (open drain). The LM49150 and the master can
communicate at clock rates up to 400kHz. Figure 2 shows the
I
stable during the HIGH period of SCL. The LM49150 is a
transmit/receive slave-only device, reliant upon the master to
generate the SCL signal. Each transmission sequence is
framed by a START condition and a STOP condition (Figure
3). Each data word, device address and data, transmitted
over the bus is 8 bits long and is always followed by an ac-
knowledge pulse (Figure 4). The LM49150 device address is
11111000.
I
The LM49150's I
I
age level set by the I
to that of the main power supply pin V
ever logic levels for the I
controller or microprocessor that is operating at a lower
supply voltage than the main battery of a portable system.
2
2
2
2
C COMPATIBLE INTERFACE
C interface timing diagram. Data on the SDA line must be
C INTERFACE POWER SUPPLY PIN (I
CV
DD
pin. The LM49150's I
2
C interface is powered up through the
2
CV
DD
2
C interface are dictated by a micro-
pin which can be set independent
2
C interface operates at a volt-
DD
2
. This is ideal when-
C compatible serial
2
CV
FIGURE 3. Start and Stop Diagram
DD
FIGURE 2. I
)
2
C Timing Diagram
16
I
The I
the transition of SDA from HIGH to LOW while SCL is HIGH,
is generated, alerting all devices on the bus that a device ad-
dress is being written to the bus.
The 7-bit device address is written to the bus, most significant
bit (MSB) first, followed by the R/W bit. R/W = 0 indicates the
master is writing to the slave device, R/W = 1 indicates the
master wants to read data from the slave device. Set R/W =
0; the LM49150 is a WRITE-ONLY device and will not re-
spond to the R/W = 1. The data is latched in on the rising edge
of the clock. Each address bit must be stable while SCL is
HIGH. After the last address bit is transmitted, the master de-
vice releases SDA, during which time, an acknowledge clock
pulse is generated by the slave device. If the LM49150 re-
ceives the correct address, the device pulls the SDA line low,
generating an acknowledge bit (ACK).
Once the master device registers the ACK bit, the 8-bit reg-
ister data word is sent. Each data bit should be stable while
SCL is HIGH. After the 8-bit register data word is sent, the
LM49150 sends another ACK bit. Following the acknowl-
edgement of the register data word, the master issues a
STOP bit, allowing SDA to go high while SCL is high.
2
C BUS FORMAT
2
C bus format is shown in Figure 4. The START signal,
300446s1
300446s0