SP6680 Datasheet, PDF (10/12 Pages) Sipex Corporation – High Efficiency Buck/Boost Charge Pump Regulator

Output Voltage Ripple with Various Input, Output and Pump Capacitors
From Tables 8, 9 & 10 it appears that increasing pump capacitance will reduce output voltage ripple
the most. But, as we saw previously in Table 7, input voltage ripple increases with increasing pump
capacitance and it is not recommended to use pump capacitors greater than the other capacitor values.
It is therefore recommended to use an output capacitor value equal to or slightly above the pump
capacitor value. Note that for most designs the SP6680 output will be followed by a Low Dropout
Regulator that will greatly reduce the output ripple.
Table 8. Output Voltage Ripple vs Input Capacitance
All Ceramic Capacitors ESR < 0.05ohm
Cout, CF1, CF2 = 2.2uF, Iout = 5mA, CLK = 32kHz
Vin = 3.55V (In Regulation)
Vin = 3.85V (Not in Regulation)
Cin (uF)
Vout Ripple mV (pp)
Vout Ripple mV (pp)
0.47
90
52
1
92
52
2.2
104
52
4.7
102
52
10
106
52
22
108
52
Table 9. Output Voltage Ripple vs Output Capacitance
All Ceramic Capacitors ESR < 0.05ohm
Cin, CF1, CF2 = 2.2uF, Iout = 5mA, CLK = 32kHz
Vin = 3.55V (In Regulation)
Vin = 3.85V (Not in Regulation)
Cout (uF)
Vout Ripple mV (pp)
Vout Ripple mV (pp)
0.47
102
64
1
102
58
2.2
104
52
4.7
102
46
10
104
44
22
102
44
Table 10. Output Voltage Ripple vs Pump Capacitance
All Ceramic Capacitors ESR < 0.05ohm
Cin, Cout = 2.2uF, Iout = 5mA, CLK = 32kHz
Vin = 3.55V (In Regulation)
Vin = 3.85V (Not in Regulation)
CF1, CF2 (uF)
Vout Ripple mV (pp)
Vout Ripple mV (pp)
0.47
365
200
1
172
108
2.2
108
52
4.7
90
24
10
76
14
22
40
8
Date: 5/25/04
SP6680 High Efficiency Buck/Boost Charge Pump Regulator
10
© Copyright 2004 Sipex Corporation