SC900
POWER MANAGEMENT
Applications Information (Cont.)
Output Voltage Code Bits:
A 5-bit linear DAC controls the output voltage of each LDO. The DAC and error-amp gain are scaled so that the LSB
size at the output is 50mV. Output voltage can be set by writing the proper code to the desired LDO register. See
Table A for the bitcodes and their corresponding voltages.
Table A - LDO Output Voltage Control Settings
Bit 4
0
0
0
0
0
-
-
1
1
Bit 3
0
0
0
0
0
-
-
1
1
Bit 2
0
0
0
0
1
-
-
1
1
Bit 1
0
0
1
1
0
-
-
1
1
Bit 0
0
1
0
1
0
-
-
0
1
LDO Output Voltage
1.45V
1.50V
1.55V
1.60V
1.65V
-
-
2.95V
3.00V
Using the I2C Interface
The SC900 is a read-write slave-mode I2C device and complies with the Philips I2C standard Version 2.1 dated
January 2000. The SC900 has six user-accessible internal 8-bit registers. The I2C interface has been designed for
program flexibility, in that once the slave address has been sent to the SC900 enabling it to be a slave transmitter/
receiver, any register can be written or read from independent of each other. While there is no auto increment/
decrement capability in the SC900 I2C logic, a tight software loop can be designed to randomly access the next
register independent of which register you begin accessing. The start and stop commands frame the data-packet
and the repeat start condition is allowed if necessary.
SC900 Limitations to the I2C Specifications
Seven-bit addressing is required for communicating with the SC900; ten-bit addressing is not allowed. Any general
call address will be ignored by the SC900. Note that the SC900 is not CBUS compatible. Finally, the SC900 can
operate in standard mode (100kbit/s) or fast mode (400kbit/s).
2005 Semtech Corp.
13
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