Modifying The Board - Analog Devices ADP5014-EVALZ User Manual

ADP5014-EVALZ User Guide
Measuring Output Voltage Ripple
To observe the output voltage ripple, place the oscilloscope probe
across the output capacitor with the probe ground lead connected
to the negative (−) capacitor terminal and the probe tip placed at
the positive (+) capacitor terminal. Set the oscilloscope to ac,
10 mV/division, 2 μs/division time base, and 20 MHz bandwidth.
A standard oscilloscope probe has a long wire ground clip. For
high frequency measurements, this ground clip picks up high
frequency noise and injects it into the measured output ripple.
Figure 3 shows an easy way to measure the output ripple properly.
Remove the oscilloscope probe sheath and wrap an unshielded
wire around the oscilloscope probe. By keeping the ground
length of the oscilloscope probe as short as possible, the true
ripple can be measured.
Figure 3. Measuring Output Voltage Ripple

MODIFYING THE BOARD

To modify the ADP5014 evaluation board configuration, unsolder,
replace, or remove the appropriate passive components or
jumpers on the board.
Changing the Output Voltages
The output voltage of the ADP5014-EVALZ evaluation board is
externally set by a resistor divider from the VREF pin to the
VSETx pin and a resistor divider from the output voltage to the
FBx pin. To limit the degradation of the output voltage accuracy
due to VSETx and FBx bias current, ensure that the bottom
resistors in the dividers are not too large.
The ADP5014 provides adjustable output voltage settings. Use
the resistor divider from the accurate internal V
voltage (VREF pin) to set the desired output voltage, and
directly tie the feedback pin (FBx) to the output when the
desired output voltage setting is less than V
desired output voltage exceeds the V
resistor divider from the output to the FBx pin to set the desired
output voltage, tie VSETx to VREF directly, and use the V
reference
REF
voltage. If the
REF
voltage, use an external
REF
REF
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reference as the error amplifier input (see the
sheet for details on output voltage programming).
The output voltage of Buck 1 of the ADP5014-EVALZ evaluation
board is preset to 1 V. Change the output voltage by replacing
the resistor divider composed of R22 and R26 when the desired
output voltage setting is less than the V
for the output voltage setting is
V = V × (R26/(R22 + R26))
OUT REF
where:
V is the output voltage.
OUT
V is the 2.0 V accurate low noise reference voltage.
REF
If the desired output voltage exceeds the V
the resistor divider composed of R5 and R6, and tie VSET1 to
VREF directly. The equation for the output voltage setting is
V = V × (1 + (R6/R5))
OUT REF
where:
V is the output voltage.
OUT
V is the 2.0 V accurate low noise reference voltage.
REF
When the output voltage is changed, the values of the inductors,
the output capacitors, and the compensation networks must be
recalculated and changed for stable operation (see the
data sheet for details on external component selection).
The method of changing the output voltage for the other
regulators is the same as for Buck 1. Table 1 shows the external
resistor dividers for each channel.
Table 1. External Resistor Dividers in Each Channel
Resistor Divider Buck 1
VSETx Divider R22, R26
FBx Divider R5, R6
Changing the Switching Frequency
The switching frequency (f
SW
evaluation board is preset to 1200 kHz. Change the switching
frequency setpoint by replacing the R4 resistor with a different
value, as shown in the following equation:
f (kHz) = 100,000/R4 (kΩ)
SW
When the switching frequency is changed, the values of the
inductors, the output capacitors, and the compensation
networks must be recalculated and changed for stable operation
(see the ADP5014 data sheet for details on external component
selection).
Changing the Function Configurations (CFG1 and CFG2)
The ADP5014 includes the CFG1 and CFG2 pins to decode the
function configurations for all channels. The CFG1 pin has
eight logic statuses that is decoded by connecting one resistor to
ground, whereas the CFG2 pin has 16 logic statuses decoded by
connecting one resistor to ground. This decoder circuitry only
works in the initiation stage of the ADP5014; therefore, the
configurations cannot be changed during operation.
The CFG1 pin programs the load output capability and parallel
operation for all channels. The value of R1 in the ADP5014-
UG-1137
ADP5014 data
voltage. The equation
REF
voltage, replace
REF
ADP5014
Buck 2 Buck 3 Buck 4
R23, R27 R24, R28 R25, R29
R9, R10 R13, R14 R18, R19
) of the ADP5014-EVALZ