EN2340QI Datasheet, PDF (13/20 Pages) Enpirion, Inc. – 204A Voltage Mode Synchronous Buck PWM

The EN2340QI 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.
The EN2340QI 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 the upper resistor of the
external feedback network (see Figure 6). Total
compensation is optimized for either low output
ripple or small solution size, and will result in a wide
loop bandwidth and excellent load transient
performance for most applications. See Table 5 for
compensation values for both options based on
input and output voltage conditions.
In some cases modifications to the compensation
may be required. The EN2340QI provides the
capability to modify the control loop response to
allow for customization for specific applications.
For more information, contact Enpirion Applications
Engineering support ([e-mail]).
R_A =
180
VOUT
(R_A in kΩ)
Round R_A up to closest
standard value higher than
the calculated value.
R_B
=
V_FB × R_A
(V_OUT − V_FB )
⎜⎜⎝⎛
V_FB is 0.75V
nominal
⎟⎟⎠⎞
Figure 6: V_OUT Resistor Divider & Compensation
Components. RA equation is only valid
for Low V_OUT ripple option. For small
solution size, see Table 5.
Input Capacitor Selection
The EN2340QI requires a 22µF/1206 input
capacitor. Low-cost, low-ESR ceramic capacitors
should be used as input capacitors for this
converter. The dielectric must be X5R or X7R
rated. Y5V or equivalent dielectric formulations
must not be used as these lose too much
capacitance with frequency, temperature and
bias voltage. In some applications, lower value
capacitors are needed in parallel with the larger,
EN2340QI
capacitors in order to provide high frequency
decoupling. Table 3 contains a list of
recommended input capacitors.
Recommended Input Capacitors
Description
22µF, 16V,
X5R, 10%,
1206
22µF, 16V,
X5R, 20%,
1206
MFG
Murata
Taiyo Yuden
P/N
GRM31CR61C226ME15
EMK316ABJ226ML-T
Table 3: Recommended Input Capacitors
Output Capacitor Selection
As seen from Table 5, the EN2340QI has been
optimized for use with either two 47µF/1206 or two
22µF/0805 output capacitors. Low ESR ceramic
capacitors are required with X5R or X7R rated
dielectric formulation. Y5V or equivalent dielectric
formulations must not be used as these lose
too much capacitance with frequency,
temperature and bias voltage. Table 4 contains a
list of recommended output capacitors
Output ripple voltage is determined by the
aggregate output capacitor impedance. Capacitor
impedance, denoted as Z, is comprised of
capacitive reactance, effective series resistance,
ESR, and effective series inductance, ESL
reactance.
Placing output capacitors in parallel reduces the
impedance and will hence result in lower ripple
voltage.
1 ₌ 1 ₊ 1 _{+ ... +} 1
Z _Total Z₁ Z ₂
Z_n
Recommended Output Capacitors
Description
47µF, 6.3V, X5R,
20%, 1206
MFG
Murata
P/N
GRM31CR60J476ME19L
47µF, 10V, X5R,
20%, 1206
Taiyo
Yuden
LMK316BJ476ML-T
22µF, 10V, X5R,
20%, 0805
Panasonic ECJ-2FB1A226M
22µF, 10V, X5R,
20%, 0805
Taiyo
Yuden
LMK212BJ226MG-T
Table 4: Recommended Output Capacitors
©Enpirion 2012 all rights reserved, E&OE
06878
Enpirion Confidential
April 16, 2012
www.enpirion.com, Page 13
Rev: B