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MAX1686

3V to 5V Regulating Charge Pumps for SIM Cards

Maxim Integrated 

3V to 5V Regulating

Charge Pumps for SIM Cards

mance with different input voltages and an additional

small 0.1µF capacitor at the output. The extra 0.1µF

capacitor improves start-up capability under full load

and reduces output ripple for high input voltages. Table

2 lists the recommended capacitor manufacturers.

Low-ESR capacitors, such as surface-mount ceramics,

decrease noise and give the best efficiency. Capaci-

tance and ESR variation over temperature need to be

taken into consideration for best performance in applica-

tions with large operating temperature ranges.

For applications where the minimum input voltage is 3V

or greater, the flying capacitor, CX, can be decreased

to 0.1µF. This provides two benefits: the inrush surge

current at start-up is reduced, and the output ripple

voltage (especially at high input voltages) is also

reduced.

Table 1. Ripple and Efficiency vs. Input

Voltage and Load Current

INPUT

VOLTAGE

(V)

2.7

2.7

3.3

3.3

3.6

3.6

4.2

4.2

LOAD

CURRENT

(mA)

1

10

1

10

1

10

1

10

VOUT RIPPLE EFFICIENCY

(mV)

(%)

30

84.3

30

86.2

60

69.5

60

70.5

80

63.2

80

63.8

120

52.3

120

52.1

Layout Considerations

High switching frequencies and large peak currents

make PC board layout an important part of design. All

capacitors should be soldered close to the IC. Con-

nect ground and power ground through a short, low-

impedance trace. Keep the extra copper on the board

and integrate it into ground as a pseudo-ground plane.

On multilayer boards, route the star ground using com-

ponent-side copper fill, then connect it to the internal

ground plane using vias. Ensure that the load is con-

nected directly across the output filter capacitor.

Table 2. Recommended Surface-Mount

Capacitor Manufacturers

VALUE

(µF)

DESCRIPTION

MFR.

PHONE

NUMBER

1 to 47

595D-series

tantalum

Sprague (603) 224-1961

4.7 to 47

TPS-series

tantalum

AVX

(803) 946-0690

1 to10

267 series

tantalum

0.047 to 2.2 X7R ceramic

Matsuo

TDK

AVX

(714) 969-2491

(847) 390-4373

(803) 946-0690

Chip Information

TRANSISTOR COUNT: 840

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