Datasheet

TPS65070, TPS65072, TPS65073
TPS650731, TPS650732, TPS650701, TPS650702, TPS650721
SLVS950G –JULY 2009–REVISED MAY 2013 www.ti.com
internal current sink at pins Isink1 and Isink2. The maximum current through the current sinks is set with two
external resistors connected from pins ISET1 and ISET2 to GND. ISET1 sets the maximum current when Bit
CURRENT LEVEL in register WLED_CTRL2 is set to 1. If this Bit is set to 0, which is the default setting, the
maximum current is defined by the resistor connected at ISET2. This allows change between two different
maximum current settings during operation. The LED current can further be dimmed with an internal PWM signal.
The duty cycle for this PWM signal can be changed with the Bits LED DUTY CYCLE 0 to LED DUTY CYCLE 6 in
register WLED_CTRL2 in a range from 1% to 100%. In case a dimming ratio higher than 1:100 is needed, the
maximum LED current need to be changed to a lower value as defined with Iset2. In order to do this without any
flicker, the PWM dimming and the current level is defined in the same register, so both settings can be changed
at the same time with a single write access to register WLED_CTRL2. An internal overvoltage protection limits
the maximum voltage at FB_wLED to 37V typically. The output voltage at FB_WLED also has a lower limit which
is set to 12V. In case less than 4LEDs are used, the output voltage at the boost converter will not drop below
12V but the voltage from ISINK1 and ISINK2 to GND is increased accordingly.
A/D Converter
The 10Bit successive approximation (SAR) A/D converter with an input multiplexer can be used to monitor
different voltages in the system. These signals are monitored:
• Battery voltage
• Voltage at AC input
• Voltage at SYS output
• Input voltage of battery charger
• Battery temperature
• Battery charge current (voltage at pin Iset; Icharge = U
ISET
/Rset × K
ISET
)
• External voltage 1 to external voltage 4 (AD_IN1 to AD_IN4); 0V to 2.25V
• Optionally: External voltage 5 to external voltage 7 (AD_IN5 to AD_IN7); 0V to 6.0V
• Internal channel AD_IN14 and AD_IN15 for touch screen measurements
The A/D converter uses an internal 2.26V reference. The reference needs a bypass capacitor for stability which
is connected to pin BYPASS. The pin can be used as a reference output with a maximum output current of
0.1mA. The internal reference voltage is forced to be on when the ADC or the touch screen interface is enabled.
The reference voltage can additionally forced to be on using Bit Vref_enable in register ADCONFIG while ADC
and touch screen are off to allow external circuits to be supplied with a precise reference voltage while ADC and
touch screen are not used.
Touch Screen Interface (only for TPS65070, TPS650701, TPS650702, TPS65073, TPS650731, TPS650732)
The touch screen itself consists of two parallel plates, called the X and Y plates, separated by short distance;
contact is initiated by using a stylus or your finger. This action creates a series of resistances noted by RX1,
RX2, RY1, RY2 , and Rcontact, shown in Figure 35. The points shown in the diagram as TSX1, TSX2, TSY1 and
TSY2 are connected to the TPS6507x touch screen interface. The resistances RX1 and RX2 scale linearly with
the x-position of the point of contact, where the RY1 and RY2 resistances scale with the y-position. The Rcontact
resistance decreases as the pressure applied at the point of contact increases and increases as the pressure
decreases. Using these relationships, the touch screen interface can make measurements of either position or
pressure.
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TPS650721