en5311qi-e Enpirion, en5311qi-e Datasheet - Page 9

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en5311qi-e

Manufacturer Part Number
en5311qi-e
Description
1a Synchronous Buck Regulator With Integrated Inductor
Manufacturer
Enpirion
Datasheet

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ALTERA
0
values is indeterminate. These pins must not
be left floating.
The External Voltage Divider pin, V
left floating for all VID settings other than the
VS0=VS1=VS2= ”1”.
External Voltage Divider
As described above, the external voltage
divider option is chosen by connecting the
VS0, VS1, and VS2 pins to V
The EN5311QI uses a separate feedback pin,
VFB, when using the external divider.
For applications with V
be connected to VOUT as indicated in Figure 4.
Figure 5 indicates the required connections for
V
Figure 4. External Divider (V
The output voltage is selected by the following
formula:
R
gain. Then R
©Enpirion 2009 all rights reserved, E&OE
V
03799
VS2
0
0
0
0
1
1
1
1
V
Table 1. VID voltage select settings.
IN
OUT
a
IN
must be chosen as 200KΩ to maintain loop
> 5.5V.
4.7uF
=
. 0
603
V
VS1
0
0
1
1
0
0
1
1
b
(
1
V
V
V
is given as:
ENABLE
V
S0
S1
S2
+
in
Ra
Rb
)
GND
IN
V
Sense
V
VS0
0
1
0
1
0
1
0
1
≤ 5.5V, VSENSE must
V
out
IN
FB
≤ 5.5V).
IN
or logic “high”.
Ra
Rb
FB,
V
Selectable
OUT
1.25V
10μF
may be
User
3.3V
2.5V
1.8V
1.5V
1.2V
0.8V
V
OUT
11/24/2009
9
V
0.6V to V
dropout voltage including margin).
Figure 5. External Divider (V
For applications where V
connection is not necessary, but the addition of
C
Dynamically Adjustable Output
The EN5311QI is designed to allow for
dynamic switching between the predefined VID
voltage levels. The inter-voltage slew rate is
optimized to prevent excess undershoot or
overshoot
transition. The slew rate is identical to the soft-
start slew rate of 1.65V/mS.
Dynamic transitioning between internal VID
settings and the external divider is not allowed.
Input and Output Capacitors
The input capacitance requirement is 4.7uF.
Enpirion recommends that a low ESR MLCC
capacitor be used. The input capacitor must
use a X5R or X7R or equivalent dielectric
formulation.
formulations lose capacitance with frequency,
bias, and with temperature, and are not
suitable for switch-mode DC-DC converter
input and output filter applications.
R
V
OUT
A
b
IN
= 27pF is required.
=
V
4.7uF
can be programmed over the range of
OUT
1
2 .
x
IN
10
. 0
603
5
– 0.6V (0.6 is the nominal full load
as
V
V
V
ENABLE
V
S0
S1
S2
Ω
in
Y5V or equivalent dielectric
the
GND
output
V
Sense
V
V
out
IN
IN
FB
www.enpirion.com
>
> 5.5V, the V
5.5V).
voltage
Ra
Rb
27pF
Ca
EN5311QI
10μF
levels
SENSE
V
Rev:B
OUT

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