DRV590_16 Datasheet, PDF (11/18 Pages) Texas Instruments – 1.2-A HIGH-EFFICIENCY PWM POWER DRIVER

DRV590
SLOS365A – AUGUST 2001 – REVISED AUGUST 2002
APPLICATION INFORMATION
LC filter in the time domain (continued)
For worst case conditions, the on-resistance of the output transistors has been ignored to give the maximum
theoretical ripple current. In reality, the voltage drop across the output transistors will decrease the maximum
V_O as the output current increases. It can be shown using equation 4 that this will decrease the inductor ripple
current, and therefore the TEC ripple current.
general operation
oscillator components R_OSC and C_OSC
The onboard ramp generator requires an external resistor and capacitor to set the oscillation frequency. For
proper operation, the resistor R_OSC should be 120 kΩ with 1% tolerance. The capacitor C_OSC should be a
ceramic 220 pF with 10% tolerance. Both components should be grounded to AGND, which should be
connected to PGND at a single point, typically where the power and ground physically connect to the printed
circuit board.
AREF capacitor
The AREF terminal is the output of an internal mid-rail voltage regulator used for the on-board oscillator and
ramp generator. The regulator may not be used to provide power to any additional circuitry. A 1-µF ceramic
capacitor must be connected from AREF to AGND for stability (see the oscillator components R_OSC and C_OSC
section for AGND connection information).
gain settings
The differential output voltage may be calculated using equation 7.
ǒ Ǔ _{VO + VOUT)–VOUT– + Av VIN)–VIN–}
(7)
Av is the voltage gain, which may be selected by configuring GAIN0 and GAIN1 according to the table below.
The input resistance also varies with the gain setting, as shown by the typical values in Table 1. Though these
values may vary by up to 30% due to process variations, the gain settings themselves vary little, as they are
determined by resistor ratios.
GAIN0
0
0
1
1
GAIN1
0
1
0
1
Table 1. Gain Settings
AMPLIFIER GAIN
(dB, TYPICAL)
6
12
18
23.5
INPUT RESISTANCE
(kΩ, TYPICAL)
104
74
44
24
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