Datasheet

V =V (R +R )/R
REGF REGS 1 2 2
·
3V
470nF
REGF
(a) (b)
REGS
3V
3V
470nF
REGF
REGS
R
1
5.6kW
REG
V
REG
R
2
8.2kW
3V
470nF
REGF
REGS
R
1
5.6kW
V
REG
VSP
220W
R
2
8.2kW
1kW
1kW
3V
REGF
REGS
R
3
47kW
5V
Source
(c) (d)
XTR111
SBOS375C –NOVEMBER 2006– REVISED JUNE 2011 www.ti.com
VOLTAGE REGULATOR The voltage at REGF is limited by the supply voltage.
If the supply voltage drops close to the set voltage,
The externally adjustable voltage regulator provides
the driver output saturates and follows the supply with
up to 5mA of current. It offers drive (REGF) and
a voltage drop of less than 1V (depending on load
sense (REGS) to allow external setting of the output
current and temperature).
voltage as shown in Figure 45. The sense input
(REGS) is referenced to 3.0V representing the lowest For good stability and transient response, use a load
adjustable voltage level. An external resistor divider capacitance of 470nF or larger. The bias current into
sets V
REGF
. the sense input (REGS) is typically less than 1μA.
This current should be considered when selecting
high resistance values for the voltage setting because
it lowers the voltage and produces additional
Table 2 provides example values for the regulator
temperature dependence.
adjustment resistors.
The REGF output cannot sink current. In case of
Table 2. Examples for the Resistor Values Setting
supply voltage loss, the output is protected against
the Regulator Voltage
the discharge currents from load capacitors by
V
REGF
(1)
R
1
R
2
internal protection diodes; the peak current should not
exceed 25mA.
3V 0 —
3.3V 3.3kΩ 33kΩ
If the voltage regulator output is not used, connect
REGF to REGS (the 3V mode) loaded with a 2.2nF
5V 5.6kΩ 8.2kΩ
capacitor. Alternatively, overdrive the loop pulling
12.4V 27kΩ 8.6kΩ
REGS high (see Figure 45d).
(1) Values have been rounded.
Figure 45. Basic Connections of the Voltage Regulator
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