HV301/HV311
Design Information, cont’d.
Programming Inrush and I
CB
, continued:
Method 2: Inrush = 1/2 I
CB
(Servo Mode)
1.
Choose I
CB
=
100mV
,
e.g. 2A
⇒
R
SENSE
= 50m
Ω
R
SENSE
Timing (Servo Mode)
contact
bounce
GND
2. Inrush =
3.
50mv
50mV
, e.g.
= 1A
R
SENSE
50m
Ω
V
IN
V
OUT
-48V
V
OUT
V
UVL
V
IN
V
GATE
Add compensation components from gate to drain if
necessary to reduce peaking.
t
START
V
RAMP
V
GATE
V
EE
t
TH
V
RAMP
V
GS(th)
V
GATE
V
GS(lim)
Capacitor and/or
compensation resistor
will reduce peaking
I
IN
t
POR
90%
I
LIM
t
RISE
t
LIM
active
t
PWRGD
PWRGD
inactive
i) start with 2nF from gate to source
ii) increase to 10nF if needed
iii) add 1k series resistor from gate to capacitor if needed
Initialization
Limiting
Full On
The timing functions are defined by the following equations:
t
START
=
2.4
C
RAMP
I
RAMP
C
RAMP
I
RAMP
t
TH
=
V
GS
(
th
)
t
POR
=
t
START
+
t
TH
t
RISE
≈
C
RAMP
I
R
g
fs
RAMP
−
SENSE
R
FB
0.9
I
LIMIT
C
LOAD
I
LIMIT
t
LIMIT
≈
V
IN
t
PWRGD
=
V
INT
−
V
GS
(
LIMIT
)
−
1.2
(
)
C
I
RAMP
RAMP
7
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