BL8516
Quiescent Current vs. Supply Voltage
3000
Feedback Voltage(V)
Quiescent Current
(uA)
1.30
1.28
1.26
1.24
1.22
1.20
0
5
10
Supply Voltage(V)
15
20
5
10
15
20
Supply
Voltage(V)
Feedback Voltage vs.Supply Voltage
2000
1000
0
Feedback Voltage vs.Temperature
1.30
Feedback Voltage(V)
1.28
Frequency(MHz)
1.26
1.24
1.22
1.20
-50
-25
0
25
Temperature
50
75
100
1.30
1.25
1.20
1.15
1.10
1.05
1.00
-50
Frequency vs.Temperature
-25
0
25
50
75
100
Temperature(ºC)
APPLICATION INFORMATION
Inductor Selection and Maximum Output
Current
The duty cycle of the internal switch is:
D = (VOUT + VD)/(VIN – VSW + VD)
In which VD is the forward voltage drop of the
catch diode (D1) and VSW is the voltage drop
of the internal switch. The value of duty cycle
at full load current is of special interest, when
values of VSW and VD can both assumed to
be 0.4V.
Since BL8516 has a maximum guaranteed
duty cycle of 88%, the minimum input voltage
is limited for a particular value of output.
When the switch is off, the voltage drop
across the inductor is equal to output voltage
plus the catch diode drop. Therefore the
peak-to-peak ripple current in the inductor
can be derived:
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5
∆IL = (1 – D)(VOUT + VD)/(L • FOSC)
In which FOSC is the switching frequency
and L is the value of the inductance. The
average inductor current is equal to the
output current and the peak inductor current
is the sum of the output current and one half
of the ripple current:
ILPK = IOUT + ∆IL /2
This current has to be kept below the
maximum allowed switch current (ILIMIT) for
output regulation. Typical values of ILIMIT are
above 2.5A and the maximum output current
is
IOUT (MAX) = ILIMIT – ∆IL/2
If the ripple current is small, then the
available output current is close to the switch
current limit. It is recommended that the
inductor value be chosen such that the peak-
BELLING [ SHANGHAI BELLING CO., LTD. ]
