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Application Note
AN-06016
Version: 1.2
Nov. 15, 2010 (Lastr
Modification Date)
Selecting correct CISSOID's regulator depending
on application
Introduction
In order to protect serial voltage regulators against short-circuit events, CISSOID’s regulator
families are internally protected in order to limit the short-circuit current. In our application
note AN-06002, it is explained that if a regulator is charged by load acting like an ideal current
source or if a resistive load is connected to an opposite voltage, then there exist some con-
straints on the regulator short-circuit current for correct startup of this device.
In order for customers to easily choose the most appropriate regulator for their applications,
the next section presents a table summarizing available CISSOID’s voltage regulators with
key points to take into account for optimal selection.
All these regulators, either positive or negative output voltage, are available in 2.5V; 3.3V; 5V;
5.5V; 9V; 10V; 12V; 13V and 15V versions. All of our regulators are currently available as die
or in TO-3 or T0-254 packages. Some additional nominal voltages between 2.5V and 15V can
be obtained when using only the TO-254 package. Please contact CISSOID if you have a
special voltage request.
Related document: AN-06002: “Voltage regulator short-circuit protection and associated po-
tential startup problem”
Selecting the most appropriate regulator
Figure 1 sketches respectively the use of a positive (CHT-LDOX) and a negative (CHT-LDNX)
voltage regulator with a generic load consisting of a grounded resistor (R
L
), an ideal current
source (I
0
) and a resistor (R
D
) connected to an opposite voltage, giving rise to a current I
D
.
The sum of these last two currents is defined as I
1
.
Table 1 summarizes the different regulator versions and their main differences. More details
can be found in respective datasheets on CISSOID’s website.
Application Note: Selecting correct CISSOID's regulator depend-
ing on application
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CHT-LDOx
V
in
I
Load
I
0
R
L
gnd
V
negative
R
D
I
D
I
RL
I
1
V
in
I
Load
I
0
R
L
gnd
V
positive
R
D
I
D
I
RL
CHT-LDNx
I
1
Figure 1: CISSOID’s “CHT” family of positive (top) and negative (bottom) voltage regulator on
a generic load.
Positive
regulators
Max I
1
before
startup
a
I
SC
(typical)
I
FB
(typical)
Static current
consumption
Line Regulation
(5V mode, typical)
CHT-LDO-xxx
b
0 mA
80 mA
2.5A
10mA
0.5mV/V
CHT-LDOS-xxx
200 mA
300mA
2.5A
3.15mA
1mV/V
CHT-LDOP-xxx
0 mA
80mA
2.5A
3.3mA
1mV/V
Negative
regulators
Max I
1
before
startup
(note1)
I
SC
(typical)
I
FB
(typical)
Static current
consumption
Min
dropout
Line Reg
(5V mode
typical)
CHT-LDN-xxx
0 mA
80 mA
2.5A
2.5mA
1.5V
1mV/V
CHT-LDNS-xxx
200 mA
700mA
2.5A
2.75mA
2.0V
1mV/V
Table 1: Different available regulators and their main differences (5V mode).
NOTES:
a
I
1
in table 1 is the current BEFORE the regulator startup. I
1
is therefore calculated assuming
that the regulator output voltage is equal to zero and assuming that the external opposite vol-
tage (V
negative
or V
positive
) is already in steady state. See below for an example of correct selec-
tion of CISSOID’s voltage regulators.
b
The “xxx” code at the end of the regulator type represents the nominal voltage in tenths of
volt. For example, CHT-LDO-033 stands for a 3.3V version, while CHT-LDO-150 stands for a
15V version.