MAX1680ESA Maxim Integrated Products, MAX1680ESA Datasheet - Page 8

• Manufacturer Part Number: MAX1680ESA
• Description: Charge Pumps 125mA f-Selct Swtchd Cap Volt Converter
• Manufacturer: Maxim Integrated Products

Specifications of MAX1680ESA

• Function: Inverting, Step Up
• Output Voltage: - 2 V to - 5.5 V, 5 V to 11 V
• Output Current: 125 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: SOIC-8 Narrow
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT

125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Table 4. Minimum Recommended Capacitances for Maximum Output Current
Figure 1. Cascading MAX1680/MAX1681s to Increase Output Voltage
Bypass the input voltage to reduce AC impedance and
to prevent internal switching noise. Bypassing depends
on the source impedance location. The AC ripple cur-
rent is 2 x I
large bypass capacitor (equal to C1) if the supply has
high AC impedance.
To produce larger negative voltages, cascade two
devices (Figure 1). For two devices, the unloaded out-
put voltage is approximately -2 x V
is reduced slightly by the first device’s output resis-
tance multiplied by the second device’s quiescent cur-
rent. The effective output resistance for a cascaded
8
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1 F
f
OSC
1000
125
250
500
NOTE: USE 4.7 F CAPACITORS FOR MAX1680.
OUT
(kHz)
for the doubler and the inverter. Use a
FSEL
CAP+
GND
CAP-
MAX1681
SHDN
1 F
OUT
LV
IN
Cascading Devices
V
+V
Bypass Capacitor
IN
INPUT
2.5
1.2
0.6
0.3
INPUT
= 2V
1 F
V
OUT
, but this value
= -V
INPUT
V
IN
CAPACITANCE (µF) (C1 = C2)
3.8
1.9
0.9
0.4
= 3V
device is larger than that for an individual device (20Ω
for two devices). Cascading several devices increases
output resistance and reduces efficiency. If a large
negative voltage is required for several stages, an
inductive inverting switching regulator such as the
MAX629 or MAX774 may offer more advantages.
Parallel two or more MAX1680/MAX1681s to reduce
output resistance voltage drop under a given load. With
reduced output resistance, paralleled devices deliver
higher load currents. Figure 2 shows two
MAX1680/MAX1681s connected in parallel. Output
resistance is inversely proportional to the number of
devices.
1 F
FSEL
CAP+
GND
CAP-
MAX1681
V
IN
SHDN
5.1
2.5
1.2
0.6
OUT
= 4V
LV
IN
Paralleling Devices
1 F
V
OUT
= -2V
V
IN
INPUT
6.4
3.2
1.6
0.8
= 5V