EN2342QI Datasheet, PDF (15/23 Pages) Altera Corporation – 4A PowerSoC Voltage Mode Synchronous PWM Buck with Integrated Inductor

Application Information
Output Voltage Programming and Loop
Compensation
The EN2342QI uses a Type IV Voltage Mode
compensation network. Type IV Voltage Mode
control is a proprietary Altera Enpirion control
scheme that maximizes control loop bandwidth to
deliver excellent load transient responses and
maintain output regulation with pin point accuracy.
For ease of use, most of this network has been
customized and is integrated within the device
package.
The EN2342QI output voltage is programmed using
a simple resistor divider network (R_A and R_B). The
feedback voltage at VFB is nominally 0.75V. R_A
depends on Table 6 and R_B can be calculated
based on Figure 8. The values recommended for
C_OUT, C_A, and R_CA make up the external
compensation of the EN2342QI. It will vary with
each PVIN and VOUT combination to optimize on
performance. The EN2342QI solution can be
optimized for either smallest size or highest
performance. Please see Table 6 for a list of
recommended R_A, C_A, R_CA, and C_OUT values for
each solution. Since VFB is a sensitive node, do
not touch the VFB node while the device is in
operation as doing so may introduce parasitic
capacitance into the control loop that causes the
device to behave abnormally and damage may
occur.
EN2342QI
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,
capacitors in order to provide high frequency
decoupling. Table 3 contains a list of
recommended input capacitors.
Recommended Input Capacitors
Description
MFG
P/N
22µF, 16V,
X5R, 10%,
Murata
GRM31CR61C226ME15
1206
22µF, 16V,
X5R, 20%,
1206
Taiyo Yuden EMK316ABJ226ML-T
Table 3: Recommended Input Capacitors
Output Capacitor Selection
As seen from Table 6, the EN2342QI 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 5 contains a list of
recommended output capacitors. In some
applications, extra bulk capacitance is required at
the load. In this case, up to 1000µF of bulk
capacitance may be used at the load as long as the
minimum ESR between the device output and the
bulk capacitance is maintained. Table 4 shows the
recommended compensation components for
applications that require bulk capacitance at the
load.
PVIN (V)
4.5 to 14
≥10
<10
VOUT (V)
≥2.5
0.6 to 1.5
1.5 to 2.5
0.6 to 1.5
1.5 to 2.5
Min. ESR
4mΩ
9mΩ
7mΩ
12mΩ
9mΩ
Compensation
COUT = 2x47µF/1206
Bulk Cap ≤ 1000µF
CA = 100pF
RA = 250kΩ
RCA = 5kΩ
Figure 8: V_OUT Resistor Divider & Compensation
Components. See Table 6 for details.
Input Capacitor Selection
The EN2342QI requires a 22µF/1206 input
capacitor. Low-cost, low-ESR ceramic capacitors
should be used as input capacitors for this
Table 4: Minimum ESR for Bulk Capacitance at Load
Note that when bulk capacitors are used the
converter must work harder during startup in order
to raise the output voltage from zero volts into
regulation. If there is too much output capacitance,
the device can hit current limit before it is able to
raise the output into regulation. If current limit is
www.altera.com/enpirion, Page 15
09520
February 21, 2014
Rev A