0

50

100

150

200

250

300

Load - mA

40

45

50

60

70

85

90

100

95

80

75

65

55

Without isolation

With isolation

TPS61093

OUT

FB

R1

R2

Cff

Option

C4

VO

C2

OUT

FB

R1

R2

Cff

Option

VO

C2

TPS61093

(a)WithisolationFET

(b)WithoutisolationFET

R1

Vout = 0.5 V

+1

R2

Vout

R1 = R2

1

0.5 V

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ö

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÷

è

ø

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TPS61093-Q1

www.ti.com

SLVSCO6 – JANUARY 2015

9.2.1.2 Detailed Design Procedure

9.2.1.2.1

Output Program

To program the output voltage, select the values of R1 and R2 (see Figure 7) according to Equation 1.

(1)

A recommended value for R2 is approximately 10-k

Ω which sets the current in the resistor divider chain to

0.5V/10k

Ω = 50-μA. The output voltage tolerance depends on the VFB accuracy and the resistor divider.

Figure 7. Resistor Divider to Program Output Voltage

9.2.1.2.2

Without Isolation FET

The efficiency of the TPS61093-Q1 can be improved by connecting the load to the VO pin instead of the OUT

pin. The power loss in the isolation FET is then negligible, as shown in Figure 8. The tradeoffs when bypassing

the isolation FET are:

•

Leakage path between input and output causes the output to be a diode drop below the input voltage when

the IC is in shutdown

•

No overload circuit protection

When the load is connected to the VO pin, the output capacitor on the VO pin should be above 1-

μF.

Figure 8. Efficiency vs. Load

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