ADP2102-0.8-EVALZ Analog Devices Inc, ADP2102-0.8-EVALZ Datasheet - Page 4

• Manufacturer Part Number: ADP2102-0.8-EVALZ
• Description: BOARD EVAL FOR ADP2102-0.8
• Manufacturer: Analog Devices Inc

Specifications of ADP2102-0.8-EVALZ

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 0.8V
• Current - Output: 600mA
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: ADP2102
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -

EVAL-ADP2102
Measuring Line Regulation
Vary the input voltage and examine the change in the output
voltage. In forced continuous conduction mode, the output
voltage ripple is small (<50 mV), but in power-save mode, the
output voltage ripple can be as large as 50 mV.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power
with the output power.
Measure the input and output voltages as close as possible to the
input and output capacitors to reduce the effect of IR drops.
Measuring Inductor Current
The inductor current can be measured by removing one end
of the inductor from its pad and connecting a current loop in
series with it. Then a current probe can be used to measure the
current flowing through the current loop, as shown in Figure 2.
MODIFYING THE EVALUATION BOARD
The ADP2102 evaluation board is supplied fully assembled and
tested for proper operation. It comes in two versions: fixed output
with output voltages ranging from 0.8 V to 1.875 V and adjustable
output with output voltages ranging from 0.8 V to 3.3 V. Refer
to the Ordering Guide for model details.
Changing the Output Voltage for the Adjustable Option
The ADP2102-x-EVALZ output regulation voltage can be changed
from 3.3 V to output voltages as low as 0.8 V by altering its
external components. The output regulation voltage of fixed
output voltage boards cannot be changed.
The output regulation voltage of adjustable voltage boards is set by
a resistive voltage divider consisting of Resistor R1 and Resistor R2.
The output regulation voltage is determined by the equation
where:
V
V
R1 is the feedback resistor from V
R2 is the feedback resistor from V
To set the output regulation voltage to the desired value, first
determine the value of the bottom resistor, R2, by
where:
V
I
STRING
OUT
FB
FB
= 0.8 V, the feedback voltage and the internal reference.
= 0.8 V, the internal reference.
V
R2 = V
is the regulated output voltage (V).
η
OUT
is the resistive divider string current (8 μA nominally).
=
V
= V
V
OUT
FB
IN
/I
FB
×
×
STRING
(1 + R1/R2)
I
I
OUT
IN
OUT
FB
to GND.
to V
FB
.
Rev. A | Page 4 of 12
Once R2 is determined, calculate the value of the top resistor,
R1, by
For example, to set the output regulation voltage of the
ADP2102-4-EVALZ to 3.0 V, calculate the value of Resistor R1
and Resistor R2.
Refer Table 1 for the recommended V
ensure stable operation.
A feedforward capacitor is required across the top resistor, R1,
for adjustable outputs greater than 1.875 V. This capacitor
provides a better transient response for medium to high load
steps. This feedforward capacitor provides additional phase
margin by creating a zero along with Resistor R1 at a frequency
given by
For example, in a 5 V input to 3.3 V output application, if the
output capacitor is 4.7 μF, a 6.8 pF feedforward capacitor is
required. This is based on a loop crossover frequency (f
150 kHz for a 4.7 μF capacitor.
Changing the Load Transient Response
The ADP2102 evaluation board load transient response can be
altered by changing the output capacitor, COUT. Ceramic
output capacitors are recommended for the ADP2102. By
default, the load transient response of the ADP2102 evaluation
board is set to 2% of the output voltage for a 600 mA load
transient. When using additional capacitance for better load
transient performance, the loss of capacitance due to dc bias
should be taken into account.
Table 1. ADP2102-x-EVALZ Configurations for V
V
(V)
0.8
1.0
1.2
1.25
1.375
1.5
1.8
1.875
2.0
2.5
3.0
3.3
OUT
R1 = R2 (V
R2 = V
R1 = R2 (V
CFF
= 100 kΩ (3.0 V − 0.8 V)/(0.8 V) = 275 kΩ
R1
(kΩ)
1
20
49.9
56.2
71.5
88.7
124
133
150
215
274
316
=
FB
(
2
/I
π
STRING
OUT
OUT
×
R1
− V
− V
R2
(kΩ)
80.6
100
100
100
100
100
100
100
100
100
100
100
= 0.8 V/8 μA = 100 kΩ
×
1
(
FB
FB
f
CO
)/(V
)/ (V
2 /
FB
CFF
(pF)
None
None
None
None
None
None
None
None
15
10
8.2
6.8
FB
)
)
)
)
OUT
L1
(μH)
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
configurations to
CIN
(pF)
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
OUT
CO
COUT
(pF)
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
) of