ATA5279 ATMEL Corporation, ATA5279 Datasheet - Page 5

• Manufacturer Part Number: ATA5279
• Manufacturer: ATMEL Corporation

3.2
9125A–RKE–04/08
Coil Driver Stage
The driver stage for each coil consists of two N-channel DMOS transistors. The low-side transis-
tor is in Darlington configuration to maintain a source-follower characteristic.
Figure 3-1.
In the graphic above, the names of internal pins have a grey shaded background, and the
hatched area is not part of the driver stage itself but only used in diagnostic mode (please refer
to the Diagnosis Block description for further information on this topic).
The driver stages are supplied by the three VDS pins, which are tied together inside the chip.
A quiescence current regulation ensures low cross current while in idle state. The output transis-
tors are monitored for current and temperature to protect them from damage caused by irregular
load conditions or too high ambient temperatures.
The driving stage is optimized for signal quality to ensure low harmonic distortions.
Two groups of driver stages are integrated: the first group is intended for high-current coils,
whereas the second group drives low-current coils. Note that there are certain coil impedance
ranges for each driver group. If the connected load exceeds this range, proper current regulation
and/or data modulation is not guaranteed.
While in idle mode and especially during a transmission, the driver stages of the five inactive
(i.e., not selected) coils are switched to high-side outputs, i.e., the positive coil connection lines
are tied to the VDS potential. The same applies to the return line inputs AxN. These measures
ensure minimum parasitic currents in the disabled coils while the selected coil is operating.
VSin_pre
Principle Driver Stage Setup
Internal nodes
GND
VDS
N
P
I
mirr
mirr1
I
HS
LS
P
mirr2
I
LS
N
pwr
ATA5279 [Preliminary]
Diag Enable
Diag Enable
I
I
HSDiag
LSDiag
Ax_State
AxP
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