ir3500v International Rectifier Corp., ir3500v Datasheet - Page 27

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

In the above equation, V
above condition is not satisfied there is a need to use a device with higher β
be used instead of a single NPN transistor.
Thermistor R
The threshold voltage of VRHOT comparator is fixed at 1.6V, and a negative temperature coefficient (NTC)
thermistor R
thermistor resistance at allowed maximum temperature T
Select the series resistor R
operational temperature range. Then calculate R
TMAX from (20).
VOLTAGE LOOP COMPENSATION
The adaptive voltage positioning (AVP) is usually adopted in the computer applications to improve the transient
response and reduce the power loss at heavy load. Like current mode control, the adaptive voltage positioning
loop introduces an extra zero to the voltage loop and splits the double poles of the power stage, which makes the
voltage loop compensation much easier.
Adaptive voltage positioning lowers the converter voltage by R
the converter. Pre-select feedback resistor R
The selection of compensation types depends on the output capacitors used in the converter. For applications
using Electrolytic, Polymer or AL-Polymer capacitors and running at lower frequency, type II compensation shown
in Figure 21(a) is usually enough. While for the applications using only ceramic capacitors and running at higher
frequency, type III compensation shown in Figure 21(b) is preferred.
VO+
VDRP
Page 27 of 34
THERM
THERM
RFB
RDRP
(a) Type II compensation
is required to sense the temperature of the power stage. If we pre-select R
and Over Temperature Setting Resistors R
R
DRP
R
R
I
( min) and V
TMAX
HOTSET
VDAC
HOTSET2
=
FB
FB
R
RCP
V
=
FB
I
1
(max)
R
Figure 21 - Voltage loop compensation network
∗
=
THERM
+
-
CCP1
R
n
(
L
to linearize the NTC thermistor, which has non-linear characteristics in the
R
∗
−
_
EAOUT
I
R
( max) is the minimum and maximum anticipated input voltage. If the
TMAX
MAX
R
0
VCCLDRV
7 .
*
O
CCP
EXP
−
*
VCCL
+
G
FB,
[
CS
R
B
and calculate the droop resistor RDRP,
THERM
HOTSET
(min)
EAOUT
HOTSET1
1
6 .
<
( *
2
)
10
T
MAX
( *
L
mA
_
VCCL
corresponding to the allowed maximum temperature
1
VO+
VDRP
MAX
is calculated from (19).
O
RFB1
*I
−
(b) Type III compensation
O,
HOTSET1
T
−
where R
_
RFB
RDRP
. 1
CFB
ROOM
CDRP
1
) 6
)]
and R
(18)
min
O
VDAC
is the required output impedance of
or Darlington configuration can
FB
RCP
HOTSET2
+
-
CCP1
(21)
EAOUT
(19)
CCP
July 03, 2008
IR3500V
THERM
(20)
EAOUT
, the NTC