ISL6421 Datasheet, PDF (8/10 Pages) Intersil Corporation – Single Output LNB Supply and Control Voltage Regulator with I2C Interface for Advanced Satellite Set-top Box Designs

ISL6421
Byte Format
Every byte put on the SDA line must be 8-bits long. The
number of bytes that can be transmitted per transfer is
unrestricted. Each byte has to be followed by an acknowledge
bit. Data is transferred with the most significant bit first (MSB).
Acknowledge
The master (microprocessor) puts a resistive HIGH level on
the SDA line during the acknowledge clock pulse (Figure 3).
The peripheral that acknowledges has to pull down (LOW)
the SDA line during the acknowledge clock pulse, so that the
SDA line is stable LOW during this clock pulse. (Of course,
set-up and hold times must also be taken into account.)
The peripheral which has been addressed has to generate
an acknowledge after the reception of each byte, otherwise
the SDA line remains at the HIGH level during the ninth
clock pulse time. In this case, the master transmitter can
generate the STOP information in order to abort the transfer.
The ISL6421 will not generate the acknowledge if the
POWER OK signal from the UVLO is LOW.
SCL
1
2
8
9
SDA
START
MSB
ACKNOWLEDGE
FROM SLAVE
FIGURE 3. ACKNOWLEDGE ON THE I²C BUS
Transmission Without Acknowledge
Avoiding detection of the acknowledgement, the
microprocessor can use a simpler transmission; it waits one
clock without checking the slave acknowledging, and sends
the new data.
This approach, though, is less protected from error and
decreases the noise immunity.
ISL6421 Software Description
Interface Protocol
The interface protocol is comprised of the following, as
shown below in Table 2:
• A start condition (S)
• A chip address byte (MSB on left; the LSB bit determines
read (1) or write (0) transmission) (the assigned I²C slave
address for the ISL6421 is 0001 00XX)
• A sequence of data (1 byte + Acknowledge)
• A stop condition (P)
TABLE 2. INTERFACE PROTOCOL
S 0 0 0 1 0 0 0 R/W ACK Data (8 bits) ACK P
Transmitted Data (I²C bus WRITE mode)
When the R/W bit in the chip is set to 0, the main
microprocessor can write on the system register (SR1) of the
ISL6421 via I²C bus. These will be written by the
microprocessor as shown below.
R, W
SR1
R, W
DCL
TABLE 3. SYSTEM REGISTER 1 (SR1)
R, W
R, W
R, W
X
ENT1
LLC1
R, W
VSEL1
R, W
EN1
R
OLF1
R, W
R, W
SR2
X
System Register Format
• R, W = Read and Write bit
• R = Read-only bit
All bits reset to 0 at Power-On
TABLE 4. SYSTEM REGISTER 2 (SR2)
R, W
R, W
R, W
R, W
R
R
X
X
X
EN2
OTF
X
TABLE 5. SYSTEM REGISTER (SR1 AND SR2) CONFIGURATION
SR
DCL ISEL1 ENT1 LLC1 VSEL1 EN1 OLF1
FUNCTION
0
1
0
0
1
SR1 is selected
0
1
0
0
1
Vout1 = 13V, Vboost1 = 13V + Vdrop
0
1
0
1
1
Vout1 = 18V, Vboost1 = 18V + Vdrop
0
1
1
0
1
Vout1 = 14V, Vboost1 = 14V + Vdrop
0
1
1
1
1
Vout1 = 19V, Vboost1 = 19V + Vdrop
0
1
0
1
22kHz tone is controlled by the DSQIN pin
0
1
1
1
22kHz tone is ON, the DSQIN input is disabled
8