Diodes ZXCT1011 - Manual (Page 7)

ZXCT1011
Issue 1- July 2005 7 www.zetex.com
© Zetex Semiconductors plc 2005
Application information (cont.)
Minimum operating voltage
The minimum operating voltage of the ZXCT1011 is 2.5V and is defined as the difference between
V
sense+
and the I
out
pin. It must be ensured that sufficient headroom is given for the operation of
the device when considering R
out
.
Figure 2 Considerations for supply rail
Voltage across device 2.5V
V
in
- V
out
2.5V
Where V
out
= I
out
x R
out
At low supply voltages and high Vsense measurements, special care must be taken to ensure the
correct operation.
The circuit in figure 2.0 shows a ZXCT1011 operating from 10V supply rail. The minimum
operating voltage of the ZXCT1011 is 2.5V. This allows a maximum output voltage of 7.5V to be
set at V
out
. A 3k resistor on the output would draw a maximum 2.5mA from Iout. - See minimum
usable supply voltage graph on page 4.
V
sense+
ZXCT
1011
sense-
V
V
in
R
sense load To
I
out
2
5 4
3.3K
V
out
R
shunt
3
R
Rshunt
120R
= 10V