HV301/HV311
Design Information, cont’d.
Programming Inrush and ICB, continued:
Timing (Servo Mode)
Method 2: Inrush = 1/2 ICB (Servo Mode)
contact
bounce
100mV
1. Choose ICB
=
, e.g. 2A ⇒ RSENSE = 50mΩ
GND
RSENSE
VOUT
VIN
VUVL
VOUT
50mv
RSENSE
50mV
50mΩ
2. Inrush =
, e.g.
=1A
VIN
-48V
VGATE
tSTART
3. Add compensation components from gate to drain if
necessary to reduce peaking.
VRAMP
VRAMP
VGATE
VGS(lim)
VGATE
VGS(th)
VEE
tTH
tPOR
Capacitor and/or
compensation resistor
will reduce peaking
ILIM
90%
IIN
tRISE
tPWRGD
tLIM
active
PWRGD
inactive
i) start with 2nF from gate to source
Initialization
Full On
Limiting
ii) increase to 10nF if needed
The timing functions are defined by the following equations:
iii) add 1k series resistor from gate to capacitor if needed
CRAMP
tSTART = 2.4
IRAMP
CRAMP
tTH = VGS(th)
IRAMP
tPOR = tSTART + tTH
CRAMP
tRISE
≈
gfs
SENSE
R
IRAMP
0.9I
−
RFB
LIMIT
CLOAD
ILIMIT
tLIMIT ≈ VIN
CRAMP
tPWRGD = V − VGS(LIMIT) −1.2
(
)
IRAMP
INT
7
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