en5366 Enpirion, en5366 Datasheet - Page 10

• Manufacturer Part Number: en5366
• Description: 6a Voltage Mode Synchronous Buck Pwm Dc-dc Converter With Integrated Inductor External Output Voltage Programming
• Manufacturer: Enpirion

September 2007
Table 1. Recommended input capacitors.
Output Capacitor Selection
The EN5366QI has been optimized for use with
approximately 50µF of output capacitance. Low
ESR ceramic capacitors are required with X5R or
X7R dielectric formulation.
dielectric formulations must not be used as these
lose capacitance with frequency, temperature
and bias voltage.
Table 2. Recommended output capacitors.
Output ripple voltage is primarily determined by
the aggregate output capacitor impedance. At
the 5MHz switching frequency output impedance,
denoted as Z, is comprised mainly of effective
series resistance, ESR, and effective series
inductance, ESL:
Z = ESR + ESL.
Placing output capacitors in parallel reduces the
impedance and will hence result in lower ripple
voltage.
Typical ripple versus capacitor arrangement is
given below:
©Enpirion 2007 all rights reserved, E&OE
Z
Total
1
Description
Description
10uF, 6.3V,
22uF, 6.3V,
47uF, 6.3V,
22uF, 10V,
47uF, 10V,
X5R, 1210
X5R, 1210
X5R, 1206
X5R, 1206
X5R, 1206
=
Z
1
1
+
Z
1
2
+
Murata
Taiyo Yuden
Murata
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
...
Murata
Murata
Murata
MFG
MFG
+
Z
1
n
GRM31CR71A476ME19L
GRM32ER71A226KE20L
GRM32ER71A476KE20L
GRM319R60J106KE19D
GRM31CR60J226KE19L
LMK325BJ226KM-T
LMK325BJ476KM-T
Y5V or equivalent
LMK316BJ106KD-T
LMK316BJ226KL-T
LMK316BJ476KL-T
P/N
P/N
10
Table 3. Output ripple vs capacitor configuration.
Compensation
The EN5366 is internally compensated through
the use of a type 3 compensation network and is
optimized for use with about 50µF of output
capacitance and will provide excellent loop
bandwidth and transient performance for most
applications. Voltage mode operation provides
high noise immunity at light load.
Voltage
impedance matching to sub 90nm loads.
In some cases modifications to the compensation
may be required. The EN5366QI provides the
capability to modify the control loop to allow for
customization for a given application. For more
information,
Engineering support.
Enable Operation
The ENABLE pin provides a means to shut down
the device, or enable normal operation. A logic
low will disable the converter and cause it to shut
down. A logic high will enable the converter into
normal operation.
asserted high, the device will undergo a normal
soft start.
Soft-Start Operation
The SS pin in conjunction with a small capacitor
between this pin and AGND provides the soft
start function to limit the in-rush current during
start-up. During start-up of the converter the
reference voltage to the error amplifier is
gradually increased to its final level by an internal
current source of typically 10uA charging the soft
start capacitor. The typical soft-start time for the
output to reach regulation voltage, from when
AVIN > V
threshold, is given by:
Output Capacitor
Configuration
5 x 10 uF
1 x 47uF
UVLO
mode
and Enable crosses its logic high
contact
control
Typical Output Ripple (mVp-p)
When the ENABLE pin is
(as measured on EN5366QI
Enpirion
Evaluation Board)
www.enpirion.com
provides
<30
<20
EN5366QI
Applications
superior
Further,