LTC3589 Linear Technology, LTC3589 Datasheet - Page 38

• Manufacturer Part Number: LTC3589
• Description: 8-Output Regulator
• Manufacturer: Linear Technology

OPERATION
Table 17. LTC3589 Read Only Status Register Table
LTC3589
Table 16. LTC3589 Command Register Table
0x32 L2DTV1 Keep-Alive
0x33 L2DTV2 LDO4 Control
THERMAL CONSIDERATIONS AND BOARD LAYOUT
Printed Circuit Board Power Dissipation
In order to ensure optimal performance and the ability
to deliver maximum output power to any regulator, it is
critical that the exposed ground pad on the backside of
the LTC3589 package be soldered to a ground plane on
the board. The exposed pad is the only GND connection
for the LTC3589. Correctly soldered to a 2500mm
plane on a double sided 1oz copper board the LTC3589
has a thermal resistance (θ
Failure to make good thermal contact between the exposed
pad on the backside of the package and an adequately
sized ground plane will result in thermal resistances far
greater than 34°C/W.
38
REG
0x02 IRQSTAT Thermal
0x13
NAME
PGSTAT
Mode:
0 = Normal
Shutdown
1 = Keep-Alive
MODE:
0 = LDO4
Enable with
EN_LDO34
1 = LDO4
Enable with
OVEN[6]
B[7]
Limit Hard
Shut Down
Occurred
LDO4 Status:
0 = V
1 = V
Good
OUT
OUT
Low
Unused
LDO4 Output Voltage:
00 = 2.8V
01 = 2.5V
10 = 1.8V
11 = 3.3V
B[6]
Near Thermal
Limit
LDO3 Status:
0 = V
1 = V
Good
JA
) of approximately 34°C/W.
OUT
OUT
Low
PGOOD
Mask:
0 = PGOOD
Low When
Slewing
1 = PGOOD
Not Changed
When
Slewing.
B[5]
Undervoltage
Hard Shut
Down
Occurred
LDO2 Status:
0 = V
1 = V
OUT
OUT
Low
Good
2
ground
LDO 2 Feedback Reference Input (V1)
LDO 2 Feedback Reference Input (V2)
B[4]
Near
Undervoltage
Limit
Buck_Boost
Status:
0 = V
1 = V
OUT
OUT
Low
Good
To ensure the junction temperature of the LTC3589 die
does not exceed the maximum rated limit and to prevent
over temperature faults, the power output of the LTC3589
must be managed by the application. The total power dis-
sipation in the LTC3589 is approximated by summing the
power dissipation in each of the switching regulators and
the LDO regulators.
The power dissipation in a switching regulator is estimated
by:
Where V
is the load current and Eff is the % effi ciency that can
P
D(SWX)
B[3]
PGOOD
Timeout Hard
Shutdown
Occurred
Step-Down
Switching
Regulator 3
Status:
0 = V
1 = V
Good
OUTX
OUT
OUT
= (V
Low
is the programmed output voltage, I
OUTX
B[2]
Unused
Step-Down
Switching
Regulator 2
Status:
0 = V
1 = V
• I
OUT
OUT
OUTX
Low
Good
)•
100 – Eff
B[1]
Unused
Step-Down
Switching
Regulator 1
Status:
0 = V
1 = V
100
OUT
OUT
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Low
Good
B[0]
Unused
LDO1 Status:
0 = V
1 = V
0001 1001
0001 1001
OUT
OUT
Low
Good
OUTX
3589p