DRV777 Datasheet, PDF (5/17 Pages) Texas Instruments – 7- bit Integrated Motor and Relay Driver

DRV777
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APPLICATION INFORMATION
SLRS062 – DECEMBER 2012
TTL and other Logic Inputs
DRV777 input interface is specified for standard 1.8V, 3V and 5V CMOS logic interface. Refer to Figure 8 and
Figure 9 to establish VOL and the corresponding typical load current levels for various input voltage ranges.
Application Information section shows an implementation to drive 1.8V relays using DRV777.
Input RC Snubber
DRV777 features an input RC snubber that helps prevent spurious switching in noisy environment. Connect an
external 1kΩ to 5kΩ resistor in series with the input to further enhance DRV777’s noise tolerance.
High-impedance Input Drivers
DRV777 features a 300kΩ input pull-down resistor. The presence of this resistor allows the input drivers to be tri-
stated. When a high-impedance driver is connected to a channel input the DRV777 detects the channel input as
a low level input and remains in the OFF position. The input RC snubber helps improve noise tolerance when
input drivers are in the high-impedance state.
On-chip Power Dissipation
Use the below equation to calculate DRV777 on-chip power dissipation P_D:
N
Ã¥ P
D
=
V
OLi
´
I
Li
i=1
Where:
N is the number of channels active together.
V_OLi is the OUT_i pin voltage for the load current I_Li.
(1)
Thermal Reliability
It is recommended to limit DRV777 IC’s die junction temperature to less than 125°C. The IC junction temperature
is directly proportional to the on-chip power dissipation. Use the following equation to calculate the maximum
allowable on-chip power dissipation for a target IC junction temperature:
( ) _{PD(MAX) =} ^T_J(MAX) ^{- T}_{A qJA}
Where:
T_J(MAX) is the target maximum junction temperature.
T_A is the operating ambient temperature.
θ_JA is the package junction to ambient thermal resistance.
(2)
Improving Package Thermal Performance
The package θ_JA value under standard conditions on a High-K board is listed in the DISSIPATION RATINGS. θ_JA
value depends on the PC board layout. An external heat sink and/or a cooling mechanism, like a cold air fan, can
help reduce θ_JA and thus improve device thermal capabilities. Refer to TI’s design support web page at
www.ti.com/thermal for a general guidance on improving device thermal performance.
Copyright © 2012, Texas Instruments Incorporated
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