HV301/HV311
10V
C
2
Design Information, cont’d.
48V
0.75nF
10A
Cload
Undervoltage/Overvoltage Operation
1
: 2
mirror
10A
GND
RAMP
GATE
Isink
V
terminal
SENSE
Termial
UV
OFF
UV
ON
Vsense
Rsense
10n=Cramp
VIN
5k
Internal Circuitry
OV
ON
OV
OFF
ꢁN
Pass
Transistor
ꢁFF
1. ChttsOVcapcua VbpOakOpV paꢂVꢂtai VOg.V8AVasVftlltws
100mV 100mV
RsOisOV= V
=
= 12.5mΩ
FptmV hOVcelcule OdVpOsas tpVveluOsV hOVꢁꢀVeidVUꢀVs ep Vuꢂ
hpOshtldVvtl egOsVceiVbOVcelcule OdVesVftlltws:
ICB
8
2. ChttsOVaipushVlOvOl,VftpVOxamꢂlOVIipush=1A
Iipush*RsOisO 1A ×12.5mΩ
R2 + R3
UVON = VUVH = 1.26 = VEEUV(on)
OVON = VOVL = 1.16 = VEEOV(on)
×
×
R1 + R2 + R3
3. Calcula OVIsaikV=
=
= 2.5µA
5kΩ
4. Calcula OVC2 daschapgOVlama
= V10µA -Isaik = 7.5µAV( yꢂacal)= aC2
5kΩ
R3
R1 + R2 + R3
WhOpOVV|ꢀEEUꢀ(ti)|VeidV|ꢀEEꢁꢀ(ti)|VVepOVUidOpV&VꢁvOpVꢀtl egOVS ep
4a. Adjus VftpVAu t-pO pyVdasablO,VafVusOdVV→
UꢂVThpOshtldVꢂtai sVpOle avOV tVꢀEE
.
ꢀ
4ꢀ
ThOi
max
≅ V
VO.g.V
V = V1.6µA
RdasablO
2.5MΩ
R1 + R2 + R3
R2 + R3
VEEUV(on) = 1.26 ×
⇒ VO.g.VaC2 =10µA -Isaik -1.6µA
487kΩ + 6.81kΩ + 9.76kΩ
6.81kΩ + 9.76kΩ
IiV hasVOxamꢂlOVwOVassumOVAu t-pO pyVasVOiablOdVstV
agitpOV1.6µA,V∴VaC2 = V10µA -Isaik = 7.5µA
VEEUV(on) = 1.26 ×
Aid
= 38.29ꢀ
= 59.85ꢀ
V
dv
dv
dt
dv
dt
5. Nt O:VVa = C VVVVVaC2 = C2
×
VVVVVIipush = Cltad ×
dt
R1 + R2 + R3
R3
VEEOV(on) = 1.16 ×
Nt OVꢀ VasVfaxOdVaidVꢀRAMPVasVctis ai VdupaigVlama aig
IN
487kΩ + 6.81kΩ + 9.76kΩ
9.76kΩ
dv
dv
=acptV ssV C a(sV hOyVshapOVa
VEEOV(on) = 1.16 ×
⇒ V VacptssV ltaCd
2V
dt
dt
ctmmtiVitdOVaidV hOapVt hOpV OpmaialsVapOVfaxOdVdupaigVaipush)
ThOpOftpO,V hOVcapcua VwallVs ep VwhOiV hOVaiꢂu VsuꢂꢂlyVvtl egOVas
aiV hOVpeigOVtfV38.29ꢀV tV59.85ꢀ.
iC2 Inrush
IipVV⇒
Cload
iC2 × Cload
=
ush =
C2
C2
byVctisOpva atiVtfVchapgOVtiVRAMPVNtdOVaC2 = 7.5µA
Programming Inrush and ICB
7.5µA × Cload
7.5µA × Cload
Iipush =
⇒ C2 =
C2
Inrush
Method 1: Inrush independent of ICB
7.5µA ×100nF
10V
Vin
C
=
= 750ꢂF = 0.75iF
2
–
+
+
–
7.5A
1A
10A
Cload=100F
inrush
Cgd
7.5A
GATE
0A
Nt OV ha VRAMPVasVꢂpt Oc OdVbyVACVdavadOpVaidVGa OV
asVclamꢂOdVai Opially.
(DRAIN)
Cdb
+ K –
RAMP
2.5A
0A
10n
VSENSE
+
Vgs
gm(Vgs-Vt)
Cgs
–
VSENSE
5k
Rsense=12.5mW
dv
df
on Cramp constant
during limiting so no
current flowing into cap
A092605
6
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