TPS60301DGS datasheet(16/22 Pages) TI

16 / 22 page

TPS60300, TPS60301, TPS60302, TPS60303

SINGLE-CELL TO 3.0-V/3.3-V, 20-mA DUAL OUTPUT,

HIGH-EFFICIENCY CHARGE PUMP

SLVS302A – DECEMBER 2000 – REVISED MARCH 2001

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

design procedure (continued)

Due to R(PG,1), an output filter can easily be formed with an output capacitor (CPG). Cut-off frequency is given

by:

ƒc +

(PG,1)

(PG)

(1)

(PG,1)

O(OUT2)

) 2pƒR

(PG,1)

(PG)

and ratio VOUT/VIN is:

(2)

with R(PG,1) = 15 Ω, C(PG) = 0.1 µF and f = 600 kHz (at nominal switching frequency)

(PG,1)

O(OUT2)

+ 0.175

Load current sourced by power-good output reduces maximum output current at OUT2. During start-up (power

good going high) current charging C(PG) will discharge C(OUT2). Therefore, C(PG) must not be larger than 0.1

C(OUT2) or the device will not start. By charging C(PG) through C(OUT2),the output voltage at OUT2 will decrease.

If the capacitance of C(PG) is to large, the circuit will detect power bad. The power-good output will go low and

discharge C(PG). Then the cycle starts again. Figure 22 shows a configuration with an LC-post filter to further

reduce output ripple and noise.

OUT1

C(OUT1)

µF

OUT2

C(OUT2)

µF

VIN

CIN

µF

INPUT

0.9 V to 1.8 V

OFF/ON

GND

TPS60300

C2F

µF

C2+

C2–

C1+

C1–

C1F

µF

VP(OUT)

Figure 22. LC-Post Filter

Table 4. Recommended Values for Lowest Output Voltage Ripple

VIN

IO(OUT2)

CIN[µF]

CXF[µF]

COUT[µF]

LP[µH]

CP[µF]

VP(OUT)

VIN

[V]

IO(OUT2)

[mA]

CERAMIC

VP(OUT)

VP–P[mV]

0.9

…1.8

1.0

0.1

0.1 (X7R)

0.9

…1.8

1.0

0.1

1 // 0.1 (X7R)

0.9

…1.8

1.0

0.1 (X7R)

0.9

…1.8

1.0

1 // 0.1 (X7R)

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