SP6680 Datasheet, PDF (7/12 Pages) Sipex Corporation – High Efficiency Buck/Boost Charge Pump Regulator

+3.6V
Lithium-Ion
Battery
4.7µF
2.2µF
2.2µF
CF1P
2
V_{IN 3}
C/4
Cx8
CLK
CF1N
9
CF2P
10
CF2N
7
SP6680
V_OUT = +5.2V to +6.3V
1
456
8
GND
2.2µF
LDO
+5.0V output
2.2µF
Figure 3. Typical SIM Card Application Circuit for the SP6680
Any standard CMOS logic output is suitable for
driving the C/4 or Cx8 control lines as long as
logic low is less than 0.4V and logic high is
greater than 1.3V.
CLK pin
not present
C/4 pin
X
Cx8 pin
X
f_PUMP
0
32.768kHz
low
low 32.768kHz
32.768kHz
low
high 262.14kHz
32.768kHz
high
low
8.192kHz
32.768kHz
high
high 262.14kHz
Table 1. Control Line Logic for the Internal Charge
Pump Oscillator
Efficiency
Power efficiency with the SP6680 charge pump
regulator is improved over standard charge pumps
doubler circuits by the inclusion of an 1.5X
output mode, as described in the Theory of
Operation section. The net result is an increase
in efficiency at battery inputs greater than 3.7 to
3.8V where the SP6680 switches to the 1.5X
mode. This is illustrated in figure 4 Efficiency vs
Input Voltage.
SP6680 Efficiency vs Battery Voltage
100
90
80
8.192kHz, Iout = 2mA
70
32.768kHz, Iout = 10mA
60
262.14kHz, Iout = 40mA
50
3.0
3.3
3.6
3.9
4.2
Battery Voltage (V)
Figure 4. Efficiency vs Battery Voltage
Capacitor Selection
In order to maintain the lowest output resistance,
input ripple voltage and output ripple voltage,
multi-layer ceramic capacitors with inherently
low ESR are recommended. Refer to Table 2 for
some suggested low ESR capacitors. Tables of
output resistance and ripple voltages for a vari-
ety of input, output and pump capacitors are
included here to use as a guide in capacitor
selection. Measured conditions are with CLK =
32kHz, 5mA output load and all capacitors are
2.2uF except when stated otherwise. A DC
power supply with added 0.25ohm output ESR
was used to simulate a Lithium Ion Battery as
shown in figure 5.
Date: 5/25/04
+
Power Supply
HP3631A
1000µF
-
0.25ohm
0.75” Leads
SP6680 EvBd
2.2µF Caps
VIN (p-p)
VOUT (p-p)
Figure 5. Capacitor Selection Test Circuit
SP6680 High Efficiency Buck/Boost Charge Pump Regulator
7
© Copyright 2004 Sipex Corporation