Infineon ICE2HS01G User Manual

Application Note 13 2011-07-06
2.3.5 Softstart time, OLP blanking time and auto-restart time
According to the definition of the softstart of the IC in the datasheet, soft start is implemented by
sweeping the operating frequency from an initial high value until the control loop takes over. The softstart
time depends on a few components, such as the
minF
R , the value of
ocp
R
and the value of
SS
C . For a
20ms target rising time of the output voltage, the customer can start with
uFC
SS
2.2
=
.
The Timer pin is used to set the blanking time
OLP
T and restart time
restart
T for over load protection. The
RC parallel circuit,
T
C and
T
R , are connected to this pin. Based on the definition in the datasheet, the
OLP blanking time with
Ω= MR
T
1 and uFC
T
1
=
can be calculated as:
ms
IR
V
CRmsT
BLT
TH
TTOLP
240)
10*20*10
4
1ln(*10*10*100020)
*
1ln(**20
66
66
=−−=−−=
−
−
The restart time can be calculated as:
ms
V
V
CRT
TH
TL
TTrestart
20301000*)
4
525.0
ln(*10*10)ln(**
66
=−=−=
−
2.3.6 Load pin setting
One of the functions of the LOAD pin is to detect the over-load or open-loop faults. Once the voltage at this pin
is higher than 1.8V, IC will start internal and external timer and determine the entering of protection mode. The
resistor divider
1FT
R and
2FT
R should be designed properly to ensure OLP is functional as required. The
bottom resistor
2FT
R connected to GND pin should be far bigger than the
FMIN
R , in order not to affect normal
regulation.
As an example, assuming
Ω
=
MR
FT
2
2
, the target voltage at Load pin is 1.82V when
overload happens. The reference voltage at frequency pin is 2V. Then the voltage at LOAD pin
V
RR
R
V
FTFT
FT
LOAD
82.12*
21
2
=
+
= [20]
We can find Ω= MR
FT
2.0
1
. A small capacitor of 1nF is usually connected to decouple noise at LOAD
pin.
2.3.7 Current sense

Infineon ICE2HS01G Specifications

General

Brand	Infineon
Model	ICE2HS01G
Category	Controller
Language	English