ir3502b International Rectifier Corp., ir3502b Datasheet - Page 31

• Manufacturer Part Number: ir3502b
• Description: Xphase3 Control Ic
• Manufacturer: International Rectifier Corp.

The VR ready delay time is
Minimum over current fault latch delay time is
VDAC Slew Rate Programming Capacitor C
Calculate the VDAC down-slope slew-rate programming capacitor from the required down-slope slew rate. The
up-slope slew rate is the same as the down-slope slew rate.
A 3.3 nF capacitor can be used. A series resistor is used to stabilize the VDAC buffer.
No Load Output Voltage Setting Resistor R
From Figure 19, the bias current of VSETPT pin is 30 uA with R
Current Report Gain and Thermal Compensation
The reporting gain specifies the max load current in form of a voltage. For this example, the 140 A represents 0.95 V
at IMON. If the thermal effects are neglected (14) can be used to find the reporting gain. However, as the inductor
DCR increases with temperature, the thermal compensation string (RTCMP1, RTCMP2, and RTHERM) can be used
to compensate this change in DCR.
Assuming T
Preselect RTCMP3=1 kΩ, and R
(16)-(23)
RTCMP1=8.837 kΩ
RTCMP2=8.457 kΩ
TD
TD
t
C
R
R
R
OCDEL
VDAC
VDAC
VSETPT
L
4
5
_
MAX



C

C

2
SS

Page 31 of 38

SS
C
SR

/
V

/
. 0
DEL
SS
I
DEL
room
I
O
SINK
I
DOWN

35
/
OCDISCHG
VSETPT
900
_
DEL
I
I
*
NLOFST
CHG
( *
CHG
=25 Deg, T
m
V
kHz
. 3
*
1
DAC


. 0
92
1 [
12
10





C
1
3850
VDAC
1 .
) 3
*
10

44
30
10
0


max
*
*
*
1 .

TD
. 0

10
10
10
*
3
=100 Deg the change in DCR is found our using (15)
*
55
* 1
53
10
/
10


4

10
3
52
6
6
10

THERM_room
*



6
10


5 .

6
6
0

6
A 50 Ω resistor is selected.
*
*
330
1 .

*
(
10

6
. 0
100
52
1
*
3 .
4
12

10
5 .

6
4 .

=10 kΩ with β

*

1
nF

6
10
1 .
25
*
. 0
VSETPT
VDAC
. 0


)]
21
6
. 0
92

ms
38
. 0

and Resistor R
mS
TD
45
THERM
m
4


. 1
=3380K RTCMP1 and RTCMP2 can be found out using
37
OSC
mS
=17.4 kΩ.
VDAC
IR3502B
V3.2