ir3092 International Rectifier Corp., ir3092 Datasheet - Page 13

• Manufacturer Part Number: ir3092
• Description: 2 Phase Opteron, Athlon, Or Vr10.x Control Ic
• Manufacturer: International Rectifier Corp.

Current Sense Amplifier
A high speed differential current sense amplifier is shown in Figure 5. Its gain decreases with increasing temperature and
is nominally 24.5 at 25ºC and 20 at 125ºC (-1400 ppm/ºC). This reduction of gain tends to compensate the 3850 ppm/ºC
increase in inductor DCR. Since in most designs the IR3092 IC junction is hotter than the inductors these two effects tend
to cancel such that no additional temperature compensation of the load line is required.
The current sense amplifier can accept positive differential input up to 75mV and negative up to -20mV before clipping.
The output of the current sense amplifier is summed with the DAC voltage which is used for over current protection,
voltage positioning and current sharing.
VCC Under Voltage Lockout (UVLO)
The VCC UVLO function monitors the IR3092’s VCC supply pin and ensures enough voltage is available to power the
internal circuitry. During power-up the fault latch is reset when VCC exceeds 7.8V and all other faults are cleared. The
fault latch is set when VCC drops below 7.3V, resulting in 500mV of nominal VCC hysteresis for powering up into a load.
5VUVL Under Voltage Lockout (5VUVL)
The 5VUVL function is provided for converters using a separate voltage supply other than VCC for gate driver bias. The
5VUVL comparator prevents operation by discharging SS/DEL and forcing EAOUT low. The 5VUVL comparator has an
OK threshold of 4.3V ensuring adequate gate drive voltage is present and a fault threshold of 4.125V.
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PWM
Ramp1
CLK1
PULSE
GATEH1
GATEL1
0.7V
EAOUT
Figure 5 – Inductor Current Sensing and Current Sense Amplifier
STEADY-STATE
OPERATION
Figure 4 – PWM Operating Waveforms
DUTY CYCLE INCREASE
DUE TO LOAD
INCREASE
CO
CSA
i
L
0.6V
L
R
s
DUTY CYCLE DECREASE DUE TO LOAD
DECREASE (BODY BRAKING) OR FAULT
v
L
R
C
v
c
L
s
V
o
C
o
STEADY-STATE
OPERATION
06/25/04
IR3092