EN5312QI Просмотр технического описания (PDF) - Altera Corporation
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EN5312QI Datasheet PDF : 16 Pages
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Table 1. VID voltage select settings.
EN5312QI
Ra must be chosen as 200KΩ to maintain loop
gain. Then Rb is given as:
R = 1.2x105 Ω
b VOUT − 0.603
VOUT can be programmed over the range of
0.6V to VIN – 0.6V (0.6 is the nominal full load
dropout voltage including margin).
VS2
VS1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
VS0
0
1
0
1
0
1
0
1
V OUT
3.3V
2.5V
1.8V
1.5V
1.25V
1.2V
0.8V
User
Selectable
VIN
4.7uF
ENABLE
Vin
VSense
Vout
VS0
VFB
VS1
VS2
GND
Ca
Ra 27pF
VOUT
10µF
Rb
Figure 5. External Divider (VIN > 5.5V).
External Voltage Divider
As described above, the external voltage
divider option is chosen by connecting the
VS0, VS1, and VS2 pins to VIN or logic “high”.
The EN5312QI uses a separate feedback pin,
VFB, when using the external divider.
For applications with VIN ≤ 5.5V, VSENSE must
be connected to VOUT as indicated in Figure
4.
Figure 5 indicates the required connections for
VIN > 5.5V.
For applications where VIN > 5.5V, the VSENSE
connection is not necessary, but the addition of
CA = 27pF is required.
Dynamically Adjustable Output
The EN5312QI 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 as the output voltage levels
transition. The slew rate is identical to the soft-
start slew rate of 1.65V/mS.
VIN
ENABLE
Vin
VSense
Vout
VOUT
Dynamic transitioning between internal VID
settings and the external divider is not allowed.
4.7uF
Ra
10µF
VS0
VFB
VS1
Rb
VS2
GND
Input and Output Capacitors
Figure 4. External Divider (VIN ≤ 5.5V).
The output voltage is selected by the following
formula:
( ) VOUT
= 0.603V
1+
Ra
Rb
The input capacitance requirement is 4.7uF.
Altera recommends that a low ESR MLCC
capacitor be used. The input capacitor must
use a X5R or X7R or equivalent dielectric
formulation. Y5V or equivalent dielectric
formulations lose capacitance with frequency,
bias, and with temperature, and are not
04535
9
December 14, 2015
www.altera.com/enpirion
Rev E
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