en5312q Enpirion, en5312q Datasheet - Page 8

• Manufacturer Part Number: en5312q
• Description: 1a Synchronous Buck Regulator With Integrated Inductor
• Manufacturer: Enpirion

March 2007
Under Voltage Lockout
During initial power up an under voltage
lockout circuit will hold-off the switching
circuitry until the input voltage reaches a
sufficient level to insure proper operation. If
the voltage drops below the UVLO threshold
the lockout circuitry will again disable the
switching.
chattering between states.
Enable
The ENABLE pin provides a means to shut
down
operation. A logic low will disable the converter
and cause it to shut down. A logic high will
Application Information
Output Voltage Select
To provide the highest degree of flexibility in
choosing output voltage, the EN5312QI uses a
3 pin VID, or Voltage ID, output voltage select
arrangement.
choose one of seven preset voltages, or to use
an external voltage divider.
output of the VID multiplexer sets the value for
the voltage reference DAC, which in turn is
connected to the non-inverting input of the
error amplifier. This allows the use of a single
feedback divider with constant loop gain and
optimum compensation, independent of the
output voltage selected.
Table 1 shows the various VS0-VS2 pin logic
states and the associated output voltage
levels. A logic “1” indicates a connection to V
or to a “high” logic voltage level. A logic “0”
indicates a connection to ground or to a “low”
logic voltage level. These pins can be either
hardwired to V
driven by standard logic levels. Logic low is
defined as V
as V
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HIGH
the
≥ 1.4V. Any level between these two
Hysteresis is included to prevent
LOW
converter
IN
This allows the designer to
or GND or alternatively can be
≤ 0.4V. Logic high is defined
or
enable
Internally, the
normal
IN
8
enable the converter into normal operation. In
shutdown mode, the device quiescent current
will be less than 1 uA.
NOTE: This pin must not be left floating.
Thermal Shutdown
When excessive power is dissipated in the
chip, the junction temperature rises. Once the
junction temperature exceeds the thermal
shutdown temperature the thermal shutdown
circuit turns off the converter output voltage
thus allowing the device to cool. When the
junction temperature decreases by 15C°, the
device will go through the normal startup
process.
values is indeterminate. These pins must not
be left floating.
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,
V
must be connected to V
Figure 4.
VS2
0
0
0
0
1
1
1
1
Table 1. VID voltage select settings.
FB
, when using the external divider. V
VS1
0
0
1
1
0
0
1
1
VS0
0
1
0
1
0
1
0
1
OUT
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as indicated in
EN5312QI
V
Selectable
OUT
1.25V
3.3V
2.5V
1.8V
1.5V
1.2V
0.8V
User
SENSE