Analog Devices Linear ADP5070 Demo Manual page 4

DEMO MANUAL SCP-ADP5070-EVALZ
VOLTAGE INPUT-TO-OUTPUT CONTROL (VIOC)
IMPLEMENTATION
To implement the VIOC function for both regulators, set
R17 and R18 to 0W, respectively. Refer to the "Configura-
tion Settings" section in the Demo Manual for the low-
dropout (LDO) linear regulator board and use the follow-
ing configuration for this board.
Table 3. VIOC Cross-Reference Designators
VIOC SETTING REFERENCES
+V Reference Designators
OUT
–V Reference Designators
OUT
Positive VIOC Equations
− V = V = 0 .8 V
V
L DOIN L DOOUT VIOC
⎛
+ R
R
= 0 .8 V
BOT
( )
V
⎝ ⎜
MAX LDOIN
I is the current through R
SINK
should be sized such that the divider current runs a mini-
mum of 100µA to minimize the I
Negative VIOC Equations
− V = V = 0 .8 V −
V
L DOIN L DOOUT VIOC
=
( )
V
MAX LDOIN
⎛
+ R + R
R
0 .8 V − BOT TOP MAX
⎝ ⎜
R
BOT
Because the V term is simply the sum of the final
LDOIN
output voltage after the LDO and the difference the
ADP5070 is adding on top, it can be helpful to take the
desired final output voltage, add (or subtract for negative
voltages) 1.0V, and then look up that voltage-resistor com-
bination from Table 2.
R can then be obtained by figuring out the difference
MAX
between the maximum and nominal output voltage of the
ADP5070, divided by the current through the internal R
resistor, which is 0.8V/R
BOT
4
R R
BOT TOP
R R
FB1 FT1
R R
FB2 FT2
⎛ ⎞
+ R
R
BOT TOP
⎝ ⎜ ⎠ ⎟
R
BOT
⎞
+ R
MAX + I
TOP
R
⎠ ⎟
SINK MAX
R
BOT
, typically 15µA, so R
MAX
error term.
SINK
⎛ ⎞
+ R
R
(
BOT TOP 1 .6 V − 0 .8 V
⎝ ⎜ ⎠ ⎟
R
BOT
⎞
( )
1 .6 V − 0 .8 V + I
R
⎠ ⎟
SINK MAX
.
FREQUENCY, SYNC AND SLEW RATE CONFIGURATION
Table 4. Slew Rate Configuration Settings
RATE
Fast
Nominal
Slow
Table 5. Frequency/Sync Configuration
RATE
2.4MHz
R
MAX 1.2MHz
R15
Clock Sync
R16
Table 6. Startup Sequence Configuration
MODE
Manual
Tracking
Seq 1–2
Seq 2–1
BOT
)
BOT
EFFICIENCY R13
Higher Open
Nominal 0W
Lower Open
R9 R10
0W Open
Open 0W
Open Open
R7 R8 EN1
Open Open High
0W Open High
__ ­
Open 0W
Open 0W Low
R14
Open
Open
0W
R11
Open
Open
0W
EN2
High
__ ­
Low
__ ­
Rev. 0