lm4570lqx National Semiconductor Corporation, lm4570lqx Datasheet - Page 8

• Manufacturer Part Number: lm4570lqx
• Description: Single-ended Input Motor Driver
• Manufacturer: National Semiconductor Corporation

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Application Information
BRIDGE CONFIGURATION EXPLANATION
The LM4570 uses a bridged architecture that drives a load
differentially. The BTL design offers several advantages over
a single-ended design. The the device outputs, V
V
polarity of the voltage across the motor can be reversed
quickly (Figure 2). A single-ended device would need to
operate from split supplies to achieve this behavior. The
ability to reverse the voltage polarity is necessary in appli-
cations where a negative (reverse polarity) pulse is used to
quickly stop the motor. If the drive voltage is just removed
from the motor (not reversed) then the motor will continue to
spin until the residual energy stored in the windings has
dissipated.
The output voltage of the LM4570 is determined by the
difference between the input voltage and V
the differential gain of the device. The output voltage is given
by the following:
O
2, both source and sink current, which means that the
FIGURE 2. Voltage Polarity and Motor Direction
REF1
, as well as
O
1 and
8
For input voltages that are less than the reference voltage,
the differential output voltage is negative. For input voltages
that are greater than the reference voltage, the differential
output voltage is positive. For example, when operating from
a 5V supply (V
6dB, with a 1V input, the voltage measured across V
V
+3V.
O
2 is -3V, with a 4V input, the differential output voltage is
REF1
V
O
1–V
= 2.5V) and with a differential gain of
O
2 = A
VD
(V
IN
–V
REF1
)
20186302
O
1 and