BD6590MUV
Technical Note
●The coil selection
The DC/DC is designed by more than 4.7µH. When L value sets to a lower value, it is possibility that the specific
sub-harmonic oscillation of current mode DC / DC will be happened. Please do not let L value to 3.3µH or below.
And, L value increases, the phase margin of DC / DC becomes to zero. Please enlarge the output capacitor value when you
increase L value.
Example)
4.7µH
6.8µH
10µH
=
=
=
output capacitor
output capacitor
output capacitor
2.2µF/50V
2.2µF/50V
2.2µF/50V
1pcs
2pcs
3pcs
This value is just examples, please made sure the final judgment is under an enough evaluation.
●The separation of the IC power supply and coil power supply
BD6590MUV can work in separating the power source in both IC power supply and coil power supply. With this application, it
can obtain that decrease of IC power consumption, and the applied voltage exceeds IC rating 7V.
That application is shown in below Fig.16. The higher voltage source is applied to the power source of coil that is connected
from 4.5V to 5.5V into IC VBAT, please follow the recommend design in Fig.16. It connects VBAT terminal and VREG
terminal together at IC outside.
When the coil power supply is applied, it is no any problem even though IC power supply is the state of 0V. Although IC
power supply is set to 0V, pull-down resistance is arranged for the power off which cuts off the leak route from coil power
supply in IC inside, the leak route is cut off. And, there is no power on-off sequence of coil power supply and IC power supply.
Adapter
Battery
4.5V to 30V
4.5V to 5.5V
10µF
4.7µH
10S × 6P
2.2µF/50V
1µF
FAILFLAG SW SW
VBAT
VBAT
1MΩ
10kΩ
PWMDRV
VDET
10KΩ
26.7kΩ
PWM
PWMPOW
fPWM=100Hz~1kHz
BD6590MUV
RESET
RSTB
TEST
LED1
LED2
LED3
LED4
LED5
LED6
OCPSET
PGND
Each 16mA
68kΩ
GND GND
ISET
27kΩ
Fig.16 Application at the time of power supply isolation (6parallel)
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2011.07 - Rev.B
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