MC34704 FREESCALE [Freescale Semiconductor, Inc], MC34704 Datasheet - Page 33

• Manufacturer Part Number: MC34704
• Description: Multiple Channel DC-DC Power Management IC
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Over-voltage Fault Register
( OVFx Register ) to indicate a fault due to over-voltage limit,
where x corresponds to each regulator from REG1 to REG8
Under-voltage Fault Register
( UVFx Register ) to indicate a fault due to under-voltage limit,
where x corresponds to each regulator from REG1 to REG8.
Thermal Shutdown Fault Register
( TSDFx Register ) to indicate a fault due to thermal limit,
where x corresponds to each regulator from REG1 to REG8,
except REG7
Regulator Fault Register
( FAULTx Register ) to indicate that a fault had occurred on
each regulator. The processor can just access this register
periodically to determine system status. This reduces the
access cycles. If a regulator fault register asserted, then the
processor can access that regulator’s registers to see what
kind of fault had occurred.
Analog Integrated Circuit Device Data
Freescale Semiconductor
The 34704 assigns a 1-bit register for each regulator
The 34704 assigns a 1-bit register for each regulator
The 34704 assigns a 1-bit register for each regulator
The 34704 assigns a 1-bit register for each regulator
FAULT
TSDF
False
False
False
False
True
OVF
True
False
SCF
True
True
UVF
True
bit
bit
bit
bit
bit
0
1
0
1
0
1
0
1
0
1
SPECIAL REGISTERS
REG3 Fine Voltage Scaling Register
that enables to lower the output voltage in 0.5% steps. The
34704 assigns an 8-bit register (REG3DAC) to the REG3
Digital to analog converter for the FB3 voltage generation.
Output votlage must be reduced gradually to avoid a OV/UV
fault to occur.
REG7 Independent ON/OFF Control (Only on 34704A)
REG7 when REG6 is not needed. Care must be taken when
turning on REG7 to avoid inrush currents during regulator
ramp-up. Following Process must be followed to assure
succesful turn on of REG7.
1. Set EN0 and clear DISCHR_B on REG7CR0 register
2. After 1ms or more, set EN1 on REG7CR0 register
3. Set REG7DAC register to $00
4. Gradually shift up REG7DAC register from $00 to $D9
Regulator 3 has an additional fine output voltage scaling
The 34704B provide two register to independently turn on
to ramp-up the output voltage in a soft-start like wave.
Soft start timing is dependant of I2C communication
speed and number of bit you change per writing, for
instance use 4,8 or 16 bits increase to ramp up the
output voltage.
55
...
1
2
3
4
5
6
REG7 independant start up example
Register Address
$58
$58
$59
$59
$59
$59
$59
...
LOGIC COMMANDS AND REGISTERS
FUNCTIONAL DEVICE OPERATION
Code
$D0
$0C
$D9
$50
$00
$04
$08
...
34704
33