A3944KLPTR-T Allegro Microsystems Inc, A3944KLPTR-T Datasheet - Page 24

• Manufacturer Part Number: A3944KLPTR-T
• Description: IC PREDRIVER MOSFET 6CH TSSOP
• Manufacturer: Allegro Microsystems Inc

Specifications of A3944KLPTR-T

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

A3944
Minimum guaranteed open load resistance
The minimum value of R
is given by the maximum value of R
load, R
For an 18 V supply this gives a minimum guaranteed open load
resistance value of 79 kΩ. This means that under all conditions,
with a load voltage of up to 18 V, a load resistance greater than
79 kΩ will always be detected as an open load. For a 36 V supply
the minimum guaranteed open load resistance value increases to
379 kΩ.
Maximum load resistance
The maximum value of R
is given by the minimum value of R
open, R
Figure 14. Open load detection limits
Lmax
Lmin
. This is defined by:
. This is defined by:
R
R
Lmax
Lmax
=
=
V
V
L
L
Lmax
Lmax
that will always be detected as an open
that will always be detected as a load
I
I
DPDmin
DPDmin
– V
– V
OLmax
OLmax
L
L
that could be detected as a
that could be detected as a
– R
– R
Dmin
Dmin
Automotive, Low Side FET Pre-Driver
(8)
(9)
For a 6 V supply this gives a maximum value of 19 kΩ for the
sum of the open load resistance and the DRNx current limit resis-
tor. This means, for example, that under all conditions, with a
DRNx current limit resistor of up to 7 kΩ, a load resistance less
than 12 kΩ will never cause an open load detection.
The two limiting values are shown in figure 14 for load volt-
ages from 6 to 36 V. Note that the load resistance value includes
the DRNx current limit resistor. In this figure, a load resistance
greater than the upper line is guaranteed to be detected as an open
load and a load resistance less than the lower line is guaranteed
not to be detected as an open load.
Practical Short to Ground Limits
A short to ground is detected, when the external FET is off, if
the voltage at the DRNx terminal is less than the short to ground
threshold, V
zero resistance and the short would be to ground at zero volts.
However in practical systems the short will have a finite resis-
tance and the power ground voltage may be higher than the refer-
ence ground of the detection circuit. The equivalent circuit during
a short to ground is shown in figure 15.
Figure 15. Short to ground detection condition
+
STG
-
V
. Under ideal conditions a short circuit would be
STG
I
DPU
V
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
OCL
DRNx
R
Dx
V
L
R
R
V
SG
L
G
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