A4402_1 ALLEGRO [Allegro MicroSystems], A4402_1 Datasheet - Page 10

• Manufacturer Part Number: A4402_1
• Description: Constant On-Time Buck Converter with Integrated Linear Regulator
• Manufacturer: ALLEGRO [Allegro MicroSystems]

A4402
The valley current must be calculated so that, at the worst-case
ripple, the converter can still supply the required current to the
load. Further information on how to calculate the ripple current is
included in the Application Information section.
ENB An active high input enables the device. When set low, the
device enters sleep mode; all internal circuitry is disabled, and the
part draws a maximum of 1 μA.
Thermal Shutdown When the device junction temperature, T
is sensed to be at T
regulator output, protecting the A4402 from damage.
Power-on Reset Delay The POR function monitors the V
voltage and provides a signal that can be used to reset a DSP or
microcontroller. A POR event is triggered by either of the follow-
ing conditions:
• V
limit on either regulator is exceeded, or if the switcher voltage
falls due to TSD.
FB2
falls below its UVLO threshold. This occurs if the current
JTSD
, a thermal shutdown circuit disables the
FB2
J
,
Constant On-Time Buck Converter
• After a rising edge on the WDI input, the voltage on TSET
reaches V
An open drain output, through the NPOR pin, is provided to
signal a POR event to the DSP or microcontroller. The reset
occurs after an adjustable delay, t
connected to the POR pin. The value of t
the following formula:
where C
Shutdown The buck regulator will shutdown if one of the fol-
lowing conditions is present:
• TSD
• ENB falling edge
with Integrated Linear Regulator
POR
TRIP
is the value of the capacitor and t
.
t
POR
= 2.4 × 102 × C
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
POR
, set by an external capacitor
POR
POR ,
is calculated using
POR
is in s.
(8)
10