EN63A0QI
Application Information
depend on the input voltage and output voltage.
Calculate the external feedback and compensation
network values with the equations below.
Output Voltage Programming and loop
Compensation
The EN63A0QI output voltage is programmed
using a simple resistor divider network. A phase
lead capacitor plus a resistor are required for
stabilizing the loop. Figure 6 shows the required
components and the equations to calculate their
values.
RA [Ω] = 48,400 x VIN [V]
*Round RA up to closest standard value
RB[Ω] = (VFB x RA) / (VOUT – VFB) [V]
VFB = 0.6V nominal
*Round RB up to closest standard value
The EN63A0QI output voltage is determined by the
voltage presented at the VFB pin. This voltage is
set by way of a resistor divider between VOUT and
AGND with the midpoint going to VFB.
CA [F] = 4.6 x 10-6 / RA [Ω]
*Round CA down to closest standard value
The EN63A0QI uses a type IV compensation
network. Most of this network is integrated.
However, a phase lead capacitor and a resistor are
required in parallel with upper resistor of the
external feedback network (Refer to Figure 6). Total
compensation is optimized for use with three 47µF
output capacitance and will result in a wide loop
bandwidth and excellent load transient performance
for most applications. Additional capacitance may
be placed beyond the voltage sensing point outside
the control loop. Voltage mode operation provides
high noise immunity at light load. Furthermore,
voltage mode control provides superior impedance
matching to ICs processed in sub 90nm
technologies.
R1 = 12kΩ
The feedback resistor network should be sensed at
the last output capacitor close to the device. Keep
the trace to VFB pin as short as possible.
Whenever possible, connect RB directly to the
AGND pin instead of going through the GND plane.
Input Capacitor Selection
The EN63A0QI has been optimized for use with
two 1206 47µF input capacitors. Low ESR ceramic
capacitors are required with X5R or X7R dielectric
formulation.
Y5V
or
equivalent
dielectric
formulations must not be used as these lose
capacitance with frequency, temperature and bias
voltage.
In some cases modifications to the compensation
or output capacitance may be required to optimize
device performance such as transient response,
ripple, or hold-up time. The EN63A0QI provides the
capability to modify the control loop response to
allow for customization for such applications. For
more information, contact Enpirion Applications
Engineering support.
In some applications, lower value ceramic
capacitors may be needed in parallel with the larger
capacitors in order to provide high frequency
decoupling. The capacitors shown in the table
below are typical input capacitors. Other capacitors
with similar characteristics may also be used.
Table 3: Recommended Input Capacitors
Description
MFG
P/N
47µF, 10V, 20%
X5R, 1206
(2 capacitors needed)
Murata
GRM31CR61A476ME19L
Taiyo Yuden
LMK316BJ476ML-T
Output Capacitor Selection
The EN63A0QI has been optimized for use with
three 1206 47µF output capacitors. Low ESR, X5R
or X7R ceramic capacitors are recommended as
the primary choice. Y5V or equivalent dielectric
formulations must not be used as these lose
capacitance with frequency, temperature and bias
voltage.
The
capacitors
shown
Recommended Output Capacitors table are typical
in
the
Figure 6: External Feedback/Compensation Network
The feedback and compensation network values
Enpirion 2012 all rights reserved, E&OE
Enpirion Confidential www.enpirion.com, Page 17
07077
May 9, 2012
Rev: C
ENPIRION [ ENPIRION, INC. ]
