ir3500v International Rectifier Corp., ir3500v Datasheet - Page 15

• Manufacturer Part Number: ir3500v
• Description: Xphase3 Vr11.1 Cpu Vtt Control Ic
• Manufacturer: International Rectifier Corp.

The voltage at the VDRP pin is a buffered version of the share bus IIN and represents the sum of the DAC voltage
and the average inductor current of all the phases. The VDRP pin is connected to the FB pin through the resistor
R
will flow into the FB pin equal to (VDRP-VSETPT) / R
voltage increases accordingly. More current flows through the feedback resistor R
lower proportional to the load current. The positioning voltage can be programmed by the resistor R
droop impedance produces the desired converter output impedance. The offset and slope of the converter output
impedance are referenced to and therefore independent of the VDAC voltage.
Remote Voltage Sensing
VOSEN+ and VOSEN- are used for remote sensing and connected directly to the load. The remote sense
differential amplifier with high speed, low input offset and low input bias current ensures accurate voltage sensing
and fast transient response.
Inductor DCR Temperature Compensation
A negative temperature coefficient (NTC) thermistor should be used for inductor DCR temperature compensation.
The thermistor should be placed close to the inductor and connected in parallel with the feedback resistor, as
shown in Figure 11. The resistor in series with the thermistor is used to reduce the nonlinearity of the thermistor.
Start-up Sequence
The IR3500V has a programmable soft-start function to limit the surge current during the converter start-up. A
capacitor connected between the SS/DEL and LGND pins controls soft start timing, over-current protection delay
and hiccup mode timing. A charge current of 52.5uA and discharge current of 4uA control the up slope and down
slope of the voltage at the SS/DEL pin respectively.
DRP
. Since the error amplifier will force the loop to maintain FB to be equal to the VSETPT, an additional current
Page 15 of 34
Figure 11 - Temperature compensation of inductor DCR
IVSETPT
Remote
Sense
Amplifier
Control IC
VDAC
VDRP
Amplifier
Error
Amplifier
+
-
-
+
+
-
DRP
VSETPT
. When the load current increases, the adaptive positioning
EAOUT
VDAC
FB
VDRP
IIN
VO
VOSEN+
VOSEN-
RSETPT
RDRP
RFB1
RFB
Rt
FB
, and makes the output voltage
July 03, 2008
IR3500V
DRP
so that the