sc900imltrt Semtech Corporation, sc900imltrt Datasheet - Page 11

• Manufacturer Part Number: sc900imltrt
• Description: Sc900 Programmable Penta Uldo With Reset And I2c Interface
• Manufacturer: Semtech Corporation

Active Shutdown
The shutdown control bits determine how the on-chip
active shutdown switches behave. Each LDO register
uses bit 5 of the LDO output voltage data byte to control
the shutdown behavior. When the active shutdown bit is
enabled (set to 1), the capacitance on the LDO output
will be discharged by an on-chip FET after the LDO is dis-
abled. When the active shutdown bit is disabled (set to
0), the output capacitance on the LDO output is dis-
charged by the load. The default active shutdown state
for all LDOs is on.
ON/OFF Control Register
Each individual LDO may be turned on or off by access-
ing the ON/OFF control register. LDOs are turned on by
setting their respective on/off bit to 1. Likewise, they
can be turned off by setting the on/off bit to 0. This
allows for on/off control with a single write command. If
the enable (EN) pin is high and data is written to the LDO
voltage registers, the LDO outputs will go to the voltage
prescribed by the Output Voltage Code bits (0-4). Data
will not be lost when toggling the on/off bit from 0 to 1.
However, if the EN pin is forced low, all circuitry in the
device is disabled. All programmed information is lost
when the enable bit is subsequently pulled high.
VASEL Pin
The VASEL pin sets the default voltage of LDO A, the
core supply. When this pin is set to VIN, the default volt-
age is 2.80V. When this pin is set to GND, the default
voltage is 1.80V. The voltage can be changed from its
default state after start up by writing to the LDO voltage
code register.
Device Addressing
Following a start condition, the master must output the
address of the slave it is accessing. The most significant
six bits of the slave are the device type identifier (ID).
For the SC900 this is fixed at 000100[B]. The next sig-
nificant bit addresses a particular device. A system can
have up to two SC900 devices on the bus. The two
addresses are defined by the state of the A0 input (see
Figure 1).
POWER MANAGEMENT
Applications Information (Cont.)
2005 Semtech Corp.
0
D
E
0
Figure 1 - Slave Address Structure
V
C I
E
T
0
Y
P
E
D I
1
E
N
T
F I
E I
0
R
0
D
P
E
P
n i
V
n i
C I
A
A
0
E
0
o t
A
o t
D
G
V
D
N
N I
D
R
E
=
=
S
1
0
S
R
/
W
X
11
When the A0 pin is tied to GND, device 1 has an address
of 0 and the combination of device type ID and address
is 0x08H. When the A0 pin is tied to VIN, device 2 has
and address of 1 and the combination of device type ID
and address is 0x09H.
The last bit of the slave address defines the operation to
be performed. When set to a one a read operation is
selected; when set to a zero a write operation is selected.
Following a start condition, the SC900 monitors the SDA
line comparing the slave address being transmitted with
its slave address (device type ID and state of A0 input).
Upon a correct compare the SC900 outputs an acknowl-
edge on the SDA line. Depending on the state of the R/
W bit, the SC900 will execute a read or write operation.
Protection Circuitry
The SC900 provides protection circuitry that prevents
the device from operating in an unspecified state. These
include Under-voltage Lockout Protection, Over-tempera-
ture Protection and Short-circuit Protection.
Under Voltage Lockout
The SC900 provides an Under Voltage Lockout (UVLO)
circuit to protect the device from operating in an unknown
state if the input voltage supply is too low. When the
battery voltage drops below the UVLO threshold, the LDOs
are disabled. As the battery voltage increases above
the hysteresis level, the LDOs are re-enabled into their
previous states, provided ENABLE has remained high. If
ENABLE goes low, the SC900 will shut down.
Over-temperature Protection
The SC900 provides an internal Over-temperature (OT)
protection circuit that monitors the internal junction tem-
perature. When the temperature exceeds the OT thresh-
old, the OT protection disables all the LDO outputs. As
the junction temperature drops below the hysteresis level
the OT protection re-enables all the LDOs in their previ-
ous states, provided ENABLE has remained high. If EN-
ABLE goes low, the SC900 will shut down.
Short-circuit Protection
Each LDO output has short-circuit protection. If a short
is applied to any output, the output voltage will drop and
the output current will be limited to the short circuit cur-
rent until the short is removed.
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SC900