DRV591 Datasheet, PDF (11/16 Pages) Texas Instruments – 3-A HIGH-EFFICIENCY PWM POWER DRIVER

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DRV591
SLOS389A – NOVEMBER 2001– REVISED MAY 2002
APPLICATION INFORMATION
VDD
10 µF
1 µF
1 µF
120 kΩ
DC Control
Voltage
1 kΩ
220 pF
1 µF
1 kΩ
Shutdown Control
AVDD
AGND (Connect to PowerPAD)
ROSC
COSC
AREF
IN+
IN–
SHUTDOWN
OUT+
PGND
PGND
PGND
PGND
PGND
PGND
OUT–
10 µH
10 µF
To TEC or Laser
Diode Anode
FAULT1
FAULT0
1 µF
10 µH
10 µF
To TEC or Laser
Diode Cathode
Figure 16. Typical Application Circuit
OUTPUT FILTER CONSIDERATIONS
TEC element manufacturers provide electrical
specifications for maximum dc current and maximum
output voltage for each particular element. The maximum
ripple current, however, is typically only recommended to
be less than 10% with no reference to the frequency
components of the current. The maximum temperature
differential across the element, which decreases as ripple
current increases, may be calculated with the following
equation:
designed for the worst-case conditions during operation,
which is typically when the differential output is at 50% duty
cycle. The following section serves as a starting point for
the design, and any calculations should be confirmed with
a prototype circuit in the lab.
Any filter should always be placed as close as possible to
the DRV591 to reduce EMI.
L
OUT+
DT
+
ǒ₁
1
) N^2Ǔ
DTmax
(1)
Where:
∆T = actual temperature differential
∆T_max = maximum temperature differential
(specified by manufacturer)
N = ratio of ripple current to dc current
OUT–
C
L
C
TEC R
Figure 17. LC Output Filter
According to this relationship, a 10% ripple current
reduces the maximum temperature differential by 1%. An
LC network may be used to filter the current flowing to the
TEC to reduce the amount of ripple and, more importantly,
protect the rest of the system from any electromagnetic
interference (EMI).
OUT+
or
OUT–
L
C
TEC R
FILTER COMPONENT SELECTION
The LC filter, which may be designed from two different
perspectives, both described below, helps estimate the
overall performance of the system. The filter should be
Figure 18. LC Half-Circuit Equivalent
(for DRV591 Only)
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