MAX871EUK-T Maxim Integrated Products, MAX871EUK-T Datasheet - Page 7

• Manufacturer Part Number: MAX871EUK-T
• Description: Charge Pumps Switched-Capacitor Voltage Inverter
• Manufacturer: Maxim Integrated Products

Specifications of MAX871EUK-T

• Function: Inverting
• Output Voltage: - 1.4 V to - 5.5 V
• Output Current: 25 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: SOT-23-5
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT

Paralleling multiple MAX870s or MAX871s reduces the
output resistance. Each device requires its own pump
capacitor (C1), but the reservoir capacitor (C2) serves
all devices (Figure 5). Increase C2’s value by a factor
of n, where n is the number of parallel devices. Figure 5
shows the equation for calculating output resistance.
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 40mA.
Under heavy loads, where higher supply is sourcing cur-
rent into OUT, the OUT supply must not be pulled above
ground. Applications that sink heavy current into OUT
require a Schottky diode (1N5817) between GND and
OUT, with the anode connected to OUT (Figure 7).
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
Figure 4. Cascading MAX870s or MAX871s to Increase
Output Voltage
C1
3
4
5
MAX870
MAX871
“1”
_______________________________________________________________________________________
Heavy Output Current Loads
Combined Doubler/Inverter
Switched-Capacitor Voltage Inverters
2
1
C1
+V
Layout and Grounding
IN
…
…
Paralleling Devices
C2
3
4
5
V
MAX870
MAX871
OUT
“n”
= -nV
IN
2
1
V
C2
OUT
Figure 5. Paralleling MAX870s or MAX871s to Reduce Output
Resistance
Figure 6. Combined Doubler and Inverter
Figure 7. High V- Load Current
C1
C1
R
OUT
=
R
NUMBER OF DEVICES
OUT
3
4
5
3
4
5
OF SINGLE DEVICE
MAX870
MAX871
“1”
MAX870
MAX871
C3
MAX870
MAX871
2
1
C1
2
1
+V
+V
GND
OUT
IN
IN
4
1
…
…
D2
D1
3
4
5
V
MAX870
MAX871
OUT
D1, D2 = 1N4148
C2
C4
“n”
= -V
V
(V
V
IN
OUT
OUT
FD1
= (2V
) - (V
= -V
2
1
IN
FD2
IN
) -
)
V
C2
OUT
7