1

2

OUT

REF

R

R * (V

/ V

1)



TPS717xx

GND

EN

NR

IN

OUT

V

IN

V

OUT

1 F

m

Ceramic

V

EN

Optional 1- F input

capacitor. May improve

source impedance, noise

or PSRR.

m

Optional 0.01- F bypass

capacitor to reduce

output noise and

increase PSRR.

m

TPS71701

GND

EN

FB

IN

OUT

V

IN

V

OUT

1 F

m

Ceramic

V

EN

R

1

R

2

Optional 1- F input

capacitor. May improve

source impedance, noise

or PSRR.

m

V

=

N

11.5

xV

OUT

V

TPS717

SBVS068H – FEBRUARY 2006 – REVISED JANUARY 2015

www.ti.com

Application Information (continued)

8.1.4 Output Noise

TPS717xx, the band gap does not contribute significantly to noise. Instead, noise is dominated by the output

resistor divider and the error amplifier input. To minimize noise in a given application, use a 0.01-

μF (minimum)

noise reduction capacitor; for the adjustable version, smaller value resistors in the output resistor divider reduce

noise. A parallel combination that gives 2.5

μA of divider current has the same noise performance as a fixed

voltage version.

(2)

8.2 Typical Applications

8.2.1 Application for Fixed Voltage Versions and Adjustable Voltage Version

Figure 33 shows the basic circuit connections for the fixed voltage options. Figure 34 gives the connections for

the adjustable output version (TPS71701). Note that the NR pin is not available on the adjustable version.

Figure 33. Typical Application Circuit

Figure 34. Typical Application Circuit

(Fixed Voltage Versions)

(Adjustable Voltage Version)

8.2.1.1 Design Requirements

Table 2 summarizes the design requirements for Figure 36.

Table 2. Design Parameters

PARAMETER

DESIGN REQUIREMENT

Input voltage

3.3 V, ±10%

Output voltage

2.8 V, ±5%

Output current

100 mA typical, 150 mA peak

Output voltage transient deviation

5%

Maximum ambient temperature

85°C

8.2.1.2 Detailed Design Procedure

For the adjustable version (TPS71701), the NR pin is replaced with a feedback (FB) pin. The voltage on this pin

for any voltage using the formula given in Equation 3:

(3)

160 k

Ω to 320 kΩ. Sample resistor values for common output voltages are shown in Table 3.

16

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