A3944KLPTR-T Allegro Microsystems Inc, A3944KLPTR-T Datasheet - Page 25

• 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
The voltage at the DRNx terminal, V
short to ground is present is defined as:
where
Note that this equation is only valid for short to ground condi-
tions when:
where V
A short to ground is detected when:
where V
Note that R
Minimum load resistance
The minimum value of R
detected is given by the maximum value of R
V
V
R
R
I
R
DPU
SG
L
D
L
G
is the load resistance,
is the load supply voltage,
is the DRNx current limit resistor.
is the ground (offset) voltage,
R
is the resistance of the short to ground (offset),
(V
(V
is the diagnostic pull-up current, and
V
L
OCL
STG
DRNx
L
L
>
R
R
– V
L
– V
L
D
+ R
+ R
is the open load clamp voltage.
is the short to ground detect voltage, then:
V
must be less than:
G
G
=
STG
) R
) R
SG
SG
(V
SG
SG
– V
V
(V
L
V
R
L
V
DRNx
– V
L
G
STG
– V
D
+ V
< V
+ R
I
– I
DPU
G
< V
L
G
) R
– V
DPU
G
STG
that will always allow a short to be
< V
SG
+ I
STG
SG
G
R
OCL
– V
)
DPU
D
+ V
G
– 1
R
– I
D
DRNx
G
< V
DPU
+ I
R
SG
, in the off-state when a
STG
DPU
R
D
L
R
that satisfies the
D
Automotive, Low Side FET Pre-Driver
(10)
(11)
Assuming worst case conditions of a maximum ground voltage
offset of +1 V and a maximum short resistance of 0.5 Ω allows
the minimum load resistance to be calculated for different load
voltages. This will be maximum at either V
ing on the relative values of R
For example, at a load voltage of 6 V and R
will be detected with a load resistance greater than 0.75 Ω when
SG = 0, or at 2.63 Ω when SG = 1. At a load voltage of 18 V the
same conditions give 0.9 Ω for SG = 0 and 0.34 Ω for SG = 1.
The limiting values for SG = 0 and SG = 1 are shown in figure 16
for load voltage from 6 to 36 V and with a DRNx current limit
resistor (R
the line is guaranteed to allow detection of a 0.5 Ω short to a
+1 V offset ground. An increase in R
Figure 16. Short to ground detection limits
short detection criterion, R
R
Lmax
=
Dmax
V
STGmin
) of 7 kΩ. In this figure, a load resistance above
– V
V
Gmax
L
– V
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Lmax
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
– I
Dmax
Gmax
., defined by:
DPUmax
and V
D
R
raises the line.
Dmax
L
.
Lmax
D
– 1
set to 5 kΩ, a short
or V
R
SGmax
Lmin
depend-
(12)
25