BD9610AMUV-E2 Datasheet, PDF (17/30 Pages) Rohm – 60V Synchronous Step-down Switching Regulator(Controller type)

BD9610AMUV
(13)About Output programmed voltage range
This IC’s Output voltage available programmed area in the application is restricted on the following graph because of
input-voltage, frequency, High-side minimum off pulse and load current.
◆About relation between frequency and input-output voltage ratio
This IC has limitation in output programmed voltage on the following graphs because of restriction of minimum pulse
for available feedback control and programmed OCP detect voltage.
20
15
Available area
10
5
Unavailable area
0
50 100 150 200 250 300 350 400 450 500
Fosc[kHz]
100
95
90
Unavailable area
85
80
75 Available area
70
65
50 100 150 200 250 300 350 400 450 500
Fosc[kHz]
Fig.34 Frequency vs input-output voltage ratio(Duty)
◆About High-side(HG) minimum off pulse
This IC has limitation in output programmed voltage on Hi-side minimum off pulse for charged BST capacitor(CBST)
because Bootstrap system is adopted.
Consider toff=600ns as OFF duty pulse.
In the case that input voltage is near output ,input voltage effects from this off pulse.
So take care of input reduced voltage limit when output programmed voltage is near input.
(ex.)Output programmed voltage Vo=12V、frequency f=250kHz (T = 1 / f = 4us)
OFF_Duty=1-Vo/Vin、minimum OFF pulse toff_min = T×OFF_Duty
Toff_min = T × (1 - Vo / Vin) = 4us × (1 - 12V / Vin) ≧ 600ns
It is necessary that Vin ≧ 14.12 [V] for holding Vo=12[V] with upper equation.
Actually consider additionally drop voltage of Ron of high-side FET, DCR of coil PCB pattern impedance.
◆About load current
There is not limitation in Vout≧10V between load current and output programmed voltage.
But it is not compliant that Vout is under 10V because of the Pre-bias sequence.
Please refer to (12)PRE-BIAS on page 16.
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TSZ22111・14・001
17/27
TSZ02201-0Q1Q0AJ00010-1-2
24.OCT.2014 Rev.002