HV301/HV311
Application Information, cont’d.
Use with Negative Ground
Current Limit Stability (Method 2 (Servo) Only)
Either the HV301 or HV311 may be used with any negative
ground systems where DC/DC PWM Converters have isolated
outputs and their inputs need not be ground referenced
(Application Circuit 14).
The closed loop current mode control system used in the HV301/
HV311 is very stable, especially when driving MOSFETs with
high gate capacitances (CISS). However, a peaking in ILIMIT near
the end of the current limit may be noted with some MOSFETs.
The current control loop can be frequency compensated to
eliminate this peaking by adding a series connected capacitor
andresistorbetweenthegateandsourceoftheexternalMOSFET.
The recommended starting values for C and R are 10nF and 1K.
These compensation values should be verified by board level
testing, which may yield satisfactory results with reduced com-
ponent values.
+48V
8
V
DD
1
PWRGD / PWRGD
R1
487kΩ
ENABLE/ ENABLE
+5V
Cload
3
2
UV
R2
6.81kΩ
HV301/
HV311
COM
OV
DC/DC PWM CONVERTER
R3
9.76kΩ
RAMP
V
4
SENSE GATE
EE
7
5
6
C1
10nF
GND
R4
12.5mΩ
Q1
IRF530
Note: capacitor may be needed to slow PWRGD dv/dt if
oscillations are observed when VIN is close to OV.
Application Circuit 14
18
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