Rainbow Electronics MAX1686H - Manual (Page 7)

MAX1686/MAX1686H
3V to 5V Regulating
Charge Pumps for SIM Cards
_______________________________________________________________________________________ 7
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, C
X , 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.
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.
2.7 1 30 84.3
2.7 10 30 86.2
3.3 1 60 69.5
3.3 10 60 70.5
3.6 1 80 63.2
3.6 10 80 63.8
4.2 1 120 52.3
4.2 10 120 52.1
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
Matsuo (714) 969-2491
0.047 to 2.2 X7R ceramic
TDK (847) 390-4373
AVX (803) 946-0690
INPUT
VOLTAGE
(V)
LOAD
CURRENT
(mA)
V
OUT
RIPPLE
(mV)
EFFICIENCY
(%)
Table 1. Ripple and Efficiency vs. Input
Voltage and Load Current
Chip Information
TRANSISTOR COUNT: 840