MAX861ISA データシートの表示（PDF） - Maxim Integrated

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MAX861ISA

50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters

Maxim Integrated 

MAX860/MAX861

50mA, Frequency-Selectable,

Switched-Capacitor Voltage Converters

Table 2. Switching-Frequency Trade-Offs

ATTRIBUTE

Output Ripple

C1, C2 Values

Supply Current

LOWER

FREQUENCY

Larger

Larger

Smaller

HIGHER

FREQUENCY

Smaller

Smaller

Larger

__________Applications Information

Capacitor Selection

The MAX860/MAX861 are tested using 10µF capacitors

for both C1 and C2, although smaller or larger values

can be used (Table 3). Smaller C1 values increase the

output resistance; larger values reduce the output

resistance. Above a certain point, increasing the

capacitance of C1 has a negligible effect (because the

output resistance becomes dominated by the internal

switch resistance and the capacitor ESR). Low-ESR

capacitors provide the lowest output resistance and

ripple voltage. The output resistance of the entire circuit

(inverter or doubler) is approximately:

ROUT = RO + 4 x ESRC1 + ESRC2 + 1 / (fS x C1)

where RO (the effective resistance of the MAX860/

MAX861’s internal switches) is approximately 8Ω and fS

is the switching frequency. ROUT is typically 12Ω when

using capacitors with 0.2Ω ESR and fS, C1, and C2 val-

ues suggested in Table 3. When C1 and C2 are so

large (or the switching frequency is so high) that the

internal switch resistance dominates the output resis-

tance, estimate the output resistance as follows:

ROUT = RO + 4 x ESRC1 + ESRC2

A typical design procedure is as follows:

1) Choose C1 and C2 to be the same, for convenience.

2) Select fS:

a) If you want to avoid a specific noise frequency,

choose fS appropriately.

b) If you want to minimize capacitor cost and size,

choose a high fS.

c) If you want to minimize current consumption,

choose a low fS.

3) Choose a capacitor based on Table 3, although

higher or lower values can be used to optimize per-

formance. Table 4 lists manufacturers who provide

low-ESR capacitors.

Table 3. Suggested Capacitor Values*

NOMINAL FREQUENCY (kHz)

C1, C2 (μF)

6

68

13

47

50

10

100

4.7

130

4.7

250

2.2

*In addition to Table 3, four graphs in the Typical

Operating Characteristics section show typical output

current for C1 and C2 capacitances ranging from

0.33µF to 22µF. Output current is plotted for inputs of

4.5V (5V - 10%) and 3.0V (3.3V - 10%), and also for

10% and 20% output droop from the ideal -VIN value.

Table 4. Low-ESR Capacitor Manufacturers

MANUFACTURER–Series

AVX TPS Series

AVX TAG Series

Matsuo 267 Series

Sprague 595 Series

Sanyo MV-GX Series

Sanyo CV-GX Series

Nichicon PL Series

United Chemicon (Marcon)

TDK

PHONE

(803) 946-0629

(803) 946-0629

(714) 969-2491

(603) 224-1961

(619) 661-6835

(619) 661-6835

(847) 843-7500

(847) 696-2000

(847) 390-4461

FAX

(803) 626-3123

(803) 626-3123

(714) 960-6492

(613) 224-1430

(619) 661-1055

(619) 661-1055

(847) 843-2798

(847) 696-9278

(847) 390-4405

COMMENTS

Low-ESR tantalum, SMT

Low-cost tantalum, SMT

Low-cost tantalum, SMT

Low-ESR tantalum, SMT

Aluminum electrolytic, through hole

Aluminum electrolytic, SMT

Aluminum electrolytic, through hole

Ceramic SMT

Ceramic SMT

Maxim Integrated

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