en5365 Enpirion, en5365 Datasheet - Page 10

• Manufacturer Part Number: en5365
• Description: 6a Voltage Mode Synchronous Buck Pwm Dc-dc Converter With Integrated Inductor 3-pin Vid Output Voltage Select
• Manufacturer: Enpirion

September 2007
Table 3. 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:
Compensation
The EN5365 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 EN5365QI provides the
©Enpirion 2007 all rights reserved, E&OE
Z
Output Capacitor
Total
1
Configuration
Description
5 x 10 uF
1 x 47uF
10uF, 6.3V,
22uF, 6.3V,
47uF, 6.3V,
X5R, 1206
X5R, 1206
X5R, 1206
=
Z
1
1
+
mode
Z
1
2
+
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
...
Murata
Murata
Murata
MFG
+
control
Typical Output Ripple (mVp-p)
Z
(as measured on EN5365QI
1
n
Evaluation Board)
GRM31CR71A476ME19L
GRM319R60J106KE19D
GRM31CR60J226KE19L
provides
LMK316BJ106KD-T
LMK316BJ226KL-T
LMK316BJ476KL-T
<30
<20
P/N
superior
Further,
10
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:
Where the soft-start time T
the soft-start capacitance C
Typically, a capacitor of around 15 nF is
recommended.
During the soft-start cycle, when the soft-start
capacitor reaches 0.75V, the output has reached
its programmed regulation range. Note that the
soft-start current source will continue to operate,
and during normal operation, the soft-start
capacitor will charge up to a final value of 2.5V.
POK Operation
The POK signal is an open drain signal from the
converter indicating the output voltage is within
the specified range. The POK signal will be a
logic high when the output voltage is within 90% -
UVLO
T
SS
= C
and Enable crosses its logic high
contact
SS
* 75KΩ (seconds)
When the ENABLE pin is
Enpirion
SS
www.enpirion.com
is in seconds and
SS
is in Farads.
EN5365QI
Applications