A6850KLTR-T(2011) 데이터 시트보기 (PDF) - Allegro MicroSystems
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A6850KLTR-T Datasheet PDF : 12 Pages
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A6850
Dual Channel Switch Interface IC
Mechanical Switch Interfacing
The A6850 can be used as an interface between mechanical
switches, set in a switch-to-ground configuration, and a low
voltage microprocessor. A series resistor must be placed in
the circuit to limit current when the mechanical switch is
closed, in order to prevent excessive power dissipation in the
A6850.
For example, to calculate the power dissipation in the A6850
driving two mechanical switches with 1 kΩ series resistors,
with VIN = 12 V, assume that the current limit for each of
the outputs is set to the maximum value, IOUTPUTM (max) =
45 mA.
When the mechanical switch is closed without a series resis-
tor, the A6850 will be at the current limit. The full 12 V of the
power supply will drop across the A6850 at 45mA The power
dissipation for one mechanical switch closed would be:
PD1 = VDrop1 × IOUTPUT1
(6)
= 12 V × 45 mA
= 540 mW
A series resistor included in the circuit reduces power dis-
sipation in the OUTPUTx section of the A6850.
The current is then limited to:
IOUTPUT1 = VIN / (35 + RSERIES)
(7)
= 12 V / 1035 Ω
= 11.59 mA
VDrop1 = 35 × IOUTPUT1
(8)
= 405.7 mV
The power dissipation in the A6850 from this switch is much
lower:
PD1 = VDrop1 × IOUTPUT1
(9)
= 0.4057 V × 11.3 mA
= 4.58 mW
VCC
VIN
Digital Output
Digital Output
Controller
Input1
Input2
VCC or
VBAT
RSENSE1
1 µF
1
3 ENABLE1
ENABLE2
5
VIN OUTPUT1 8
2 SENSE1
4
SENSE2
A6850
6
OUTPUT2
RSENSE2
GROUND
7
Wiring Harness
RSERIES
RSERIES
Figure 6. Typical Application with Mechanical Switches
Allegro MicroSystems, Inc.
9
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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