LMD18201T National Semiconductor, LMD18201T Datasheet - Page 9

• Manufacturer Part Number: LMD18201T
• Description: IC, MOTOR CTRL, HALF BRIDGE 3A TO-220-11
• Manufacturer: National Semiconductor

Specifications of LMD18201T

• Motor Type: Half Bridge
• No. Of Outputs: 2
• Output Current: 3A
• Supply Voltage Range: 12V To 55V
• Driver Case Style: TO-220
• No. Of Pins: 11
• Operating Temperature Range: -40°C To +125°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

CURRENT SENSING
In many motor control applications it is desirable to sense and
control the current through the motor. For these types of ap-
plications a companion product, the LMD18200, is also avail-
able. The LMD18200 is identical to the LMD18201 but has
current sensing transistors that output a current directly pro-
portional to the current conducted by the two upper DMOS
power devices to a separate current sense pin. This technique
does not require a low valued, power sense resistor and does
not subtract from the available voltage drive to the motor.
To sense the bridge current through the LMD18201 requires
the addition of a small sense resistor between the power
ground/sense pin (Pin 7) and the actual circuit ground (see
Figure
8). This resistor should have a value of 0.1Ω or less to
FIGURE 7. Basic Motor Driver
FIGURE 8. Current Sensing
9
stay within the allowable voltage compliance of the sense pin,
particularly at higher operating current levels. The voltage be-
tween power ground/sense (Pin 7) and the signal ground (Pin
8) must stay within the range of −1V to +0.5V. Internally there
is approximately 25Ω between pins 7 and 8 and this resis-
tance will slightly reduce the value of the external sense
resistor. Approximately 70% of the quiescent supply current
(10 mA) flows out of pin 7. This will cause a slight offset to the
voltage across the sense resistor when the bridge is not con-
ducting. During reverse recovery of the internal protection
diodes the voltage compliance between pins 7 and 8 may be
exceeded. The duration of these spikes however are only ap-
proximately 100 ns and do not have enough time or energy
to disrupt the operation of the LMD18201.
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