EN5330 データシートの表示（PDF） - Enpirion, Inc.
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EN5330 Datasheet PDF : 11 Pages
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Rev 1.0 – July 2005
EN5330
Theory of Operation
Synchronous Buck Converter
The EN5330 is a synchronous, pin programmable
power supply with integrated power MOSFET
switches and inductor. The nominal input voltage
range is 2.5V-5.0V. The output can be set to common
voltages by connecting appropriate combinations of 3
voltage selection pins to ground. If different voltage
levels are required, provision is also made to allow
external programming. The feedback control loop is
voltage-mode and the part uses a low-noise PWM
topology. Up to 3A of output current can be drawn
from this converter. The 5MHz operating frequency
enables the use of small-size output capacitors.
It is recommended that Rb1 and Rb2 resistor values
be ~2kΩ. Use the following equation to set the
resistor Ra1 for the desired output voltage:
Ra1 = (Vout − 0.8V ) * Rb1
0.8V
If over-voltage protection is desired, use the following
equation to set the resistor Ra2 for the desired OVP
trip-point:
Ra2 = (OVPtrip − 0.96V ) * Rb2
0.96V
The power supply also has protection features such as:
• Programmable over-current protection (to
protect the IC from excessive load current)
• Thermal shutdown (to protect the converter
from getting too hot)
• Over-voltage protection that stops the PWM
switching and turns on the lower N-MOSFET
at 120% of the programmed output voltage in
order to protect the load from an OV
condition.
• Under-voltage lockout circuit to disable the
converter output when the input voltage is less
than approximately 2.2V
By design, if both resistor dividers are the same, the
OV trip-point will be 20% above the nominal output
voltage.
Figure 1: External output voltage and OVP setting
22µF
PVIN VOUT
AVIN
Ra2
PGND
XOV
XFB
SS
VOUT
Ra1
Rb2
Rb1
15 nF
47µF
PGND
AGND
AGND
Additional features include:
• Soft-start circuit, limiting the in-rush current
when the converter is powered up.
• Power good circuit indicating whether the
output voltage is within 90%-120% of the
programmed voltage.
Output Voltage Programming
The EN5330 output voltage is programmed using one
of two methods. Common output voltages are
achieved by tying one or more of the three Voltage
Select pins (VS0, VS1 & VS2) to ground (see Table
1). If all three are left floating, the output voltage and
over voltage thresholds are determined by the voltages
presented at the XFB and XOV pins respectively.
These voltages should be set by way of resistor
dividers between VOUT to AGND with the midpoint
going to XFB and XOV (See Figure 1).
Table 1: Output Voltage Select Table
VS2* VS1* VS0* Output Voltage
0
0
0
3.3V
0
0
1
2.5V
0
1
0
1.8V
0
1
1
1.5V
1
0
0
1.25V
1
0
1
1.2V
1
1
0
0.8V**
1
1
1 User Selectable
** 0.8V ref only, not guaranteed performance
* The VS0, VS1 and VS2 pins are defaulted to a ‘1’
with an internal pull-up resistor. Only connect
these pins to AGND if a ‘0’ is required. If a ‘1’ is
required, then leave the pin floating.
7
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