Datasheet

DRV8662
www.ti.com SLOS709A –JUNE 2011–REVISED NOVEMBER 2012
DETAILED DESCRIPTION
OPERATION
The DRV8662 accepts the typical battery range used in portable applications (3.0 V to 5.5 V) and creates a
boosted supply rail with an integrated DC-DC converter. This boosted supply rail is fed to an internal, high-
voltage, fully-differential amplifier that is capable of driving capacitive loads such as piezos with signals up to
200 V
PP
. No transformer is required for boost operation. Only a single inductor is needed. The boost power FET
and power diode are both integrated within the device.
FAST START-UP (ENABLE PIN)
The DRV8662 features a fast startup time, which is essential for achieving low latency in haptic applications.
When the EN pin transitions from low to high, the boost supply is turned on, the input capacitor is pre-charged,
and the amplifier is enabled in a typical 1.5 ms total startup time. In the system application, the entire system
latency should be kept to less than 30 ms total to be imperceptible to the end user. At 1.5 ms, the DRV8662 will
be a small percentage of the total system latency.
GAIN CONTROL
The gain from IN+/IN– to OUT+/OUT– is given by the table below.
GAIN1 GAIN0 Gain (dB)
0 0 28.8
0 1 34.8
1 0 38.4
1 1 40.7
The gains are optimized to achieve approximately 50 V
PP
, 100 V
PP
, 150 V
PP
, or 200 V
PP
at the output without
clipping from a 1.8 V peak single-ended input signal source.
ADJUSTABLE BOOST VOLTAGE
The output voltage of the integrated boost converter may be adjusted by a resistive feedback divider between the
boost output voltage (VBST) and the feedback pin (FB). The boost voltage should be programmed to a value
greater than the maximum peak signal voltage that the user expects to create with the DRV8662 amplifier. Lower
boost voltages will achieve better system efficiency when lower amplitude signals are applied, so the user should
take care not to use a higher boost voltage than necessary. The maximum allowed boost voltage is 105V.
ADJUSTABLE BOOST CURRENT LIMIT
The current limit of the boost switch may be adjusted via a resistor to ground placed on the REXT pin. The
programmed current limit should be less than the rated saturation limit of the inductor selected by the user to
avoid damage to both the inductor and the DRV8662. If the combination of the programmed limit and inductor
saturation is not high enough, then the output current of the boost converter will not be high enough to regulate
the boost output voltage under heavy load conditions. This will, in turn, cause the boosted rail to sag, possibly
causing distortion of the output waveform.
INTERNAL CHARGE PUMP
The DRV8662 has an integrated charge pump to provide adequate gate drive for internal nodes. The output of
this charge pump is placed on the VPUMP pin. An X5R or X7R storage capacitor of 0.1 µF with a voltage rating
of 10 V or greater must be placed at this pin.
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