Technical Note
BA6956AN,BA6287F,BA6285FS,BA6285AFP-Y,BA6920FP-Y
2) Output high voltage setting
This function optionally sets output voltage by the output high voltage setting pin and controls the motor rotating speed.
However, when the output high voltage is set to a low level, consumption at IC increases. Carry out thermal design with
sufficient margin incorporated with the power dissipation (Pd) under the actual application condition taken into account.
a) BA6287F, BA6285FS, BA6285AFP-Y
VM
The circuit diagram associated with the output high voltage setting
VREF pin is as per shown on the right. The output high and low
VREF
voltages VOH and VOL are expressed by:
Q1
Q2
VOH = VREF - ( VSAT(Q1) + VF(Q2)
OL = VSAT(Q3)
)
V
OUT
(Reference values; VSAT ≈ 0.15V, VF ≈ 0.7V)
Q3
In addition, the relation of VREF voltage to output voltage is expressed by:
( VSAT(Q1) + VF(Q2) ) < VREF < VM - VSAT(Q2) + VF(Q2) + VSAT(Q1)
RNF
(GND, BA6287F)
Fig.35 BA6287F, BD6285FS, BA6285AFP-Y
Therefore, when the VREF voltage condition is as follows, the
output high voltage is restricted.
VREF > VM - VSAT(Q2) + VSAT(Q1) + VF(Q2)
VOH = VM - VSAT(Q2)
VM
VM
b) BA6956AN, BA6920FP-Y
VCC
VCC
The circuit diagram associated with the output high
voltage setting VREF pin is as per shown on the right.
The output high and low voltages VOH and VOL are
expressed by:
Q1
Q4
Q1
Q4
Q2
Q2
Q7
Q3
Q6
Q3
Q6
OUT
OUT
RNF
V
OH = VREF + ( VF(Q5) + VF(Q4) ) - ( VF(Q2) + VF(Q3)
VOH ≈ VREF
OL = VSAT(Q6) (BA6956AN)
)
VREF
Q5
VREF
Q5
V
VOL = VSAT(Q7) + VF(Q6) (BA6920FP-Y)
RNF
(Reference values; VSAT ≈ 0.15V, VF ≈ 0.7V)
Fig.36 BA6956AN
Fig.37 BA6920FP-Y
The output high voltage controllable range is expressed by:
VREF < VCC - VSAT(Q1) - VF(Q4) - VF(Q5)
VREF < VM - ( VSAT(Q2) + VF(Q3) ) + ( VF(Q2) + VF(Q3)) - ( VF(Q4) + VF(Q5) ) (BA6956AN)
VREF < VM - VSAT(Q3) + ( VF(Q2) + VF(Q3)) - ( VF(Q4) + VF(Q5) ) (BA6920FP-Y)
When the VREF voltage condition is as follows, the output high voltage is restricted.
VREF > VCC - VSAT(Q1) - VF(Q4) - VF(Q5)
VREF > VM - ( VSAT(Q2) + VF(Q3) ) + ( VF(Q2) + VF(Q3)) - ( VF(Q4) + VF(Q5) ) (BA6956AN)
VREF > VM - VSAT(Q3) + ( VF(Q2) + VF(Q3)) - ( VF(Q4) + VF(Q5) ) (BA6920FP-Y)
VOH = VCC - VSAT(Q1) - VF(Q2) - VF(Q3)
V
OH = VM - VSAT(Q2) - VF(Q3) (BA6956AN)
VOH = VM - VSAT(Q3) (BA6920FP-Y)
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2011.05 - Rev.B
12/17
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