DRV595 Datasheet, PDF (10/24 Pages) Texas Instruments – 15V/±3A High-Efficiency PWM Power Driver

DRV595
SLOS808 – DECEMBER 2012
APPLICATION INFORMATION
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OUTPUT FILTER CONSIDERATIONS
The DRV595 can be used to drive a TEC element. The typical circuit used for this application is to have two
feedback loops – one for constant current, and the second to monitor the temperature, and provide adjustments
to keep a constant temperature on the laser diode. An error amplifier is used to combine the two feedback loops,
along with a control signal from the system. The output of the error amplifier is then fed into the DRV595.
An output filter needs to be used to prevent excessive ripple from reaching the TEC element. Some TEC
elements may be damaged by ripple; design the filter using the TEC specification to reduce the switching
waveform enough to prevent TEC damage. This filter also reduces the amount of electrical noise coupled onto
the TEC element.
For most applications, a second-order Butterworth low-pass filter with the cut-off frequency set to a few kilohertz
should be sufficient. See Figure 12 for example filter designed with Equation 2, Equation 3, and Equation 4 .
Second-Order Butterworth LPF Transfer Function
H(s) =
s²
+
1
2s + 1
(1)
Using Half-Circuit Analysis
L1
C1
3.3 µF
L2
T
CF
E
C
C2
3.3 µF
Figure 12. Second Order Butterworth Low-Pass Filter Configuration
L_x =
2 ´ R_L
2w_o
(2)
2
2 ´ C_F
=
2´
R_L
2
´
w₀
(3)
w₀ = 2p ´ ƒ
(4)
10
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