ZXCT1107_1107 DIODES [Diodes Incorporated], ZXCT1107_1107 Datasheet - Page 13

• Manufacturer Part Number: ZXCT1107_1107
• Description: LOW POWER HIGH-SIDE CURRENT MONITORS
• Manufacturer: DIODES [Diodes Incorporated]

A Product Line of
Diodes Incorporated
ZXCT1107/1109/1110
LOW POWER HIGH-SIDE CURRENT MONITORS
Application Information
(cont.)
Alternatively, the ZXCT1110 may be used with a reduced sense voltage if desired. From Equation 3, with ε=4%,
. 0
082
=
V
= 0.082/(4-1.8) = 37.2mV
SENSE
ε
−
1
8 .
Equation 4 gives
R
= 37.2mV/2A = 18.6mΩ
SENSE
A suitable preferred value is 20mΩ. Then the sense voltage will be 2A * 20mΩ = 40mV.
Equation 5 gives
2
=
R
= 12500Ω
GAIN
. 0
004
*
. 0
04
A suitable preferred value is 13kΩ.
The alternative example circuit using the ZXCT1110 with a sense voltage of 40mV is shown in Figure 3, giving the required
overall accuracy of ±6%.
20mΩ
I
V
LOAD
SUPPLY
S+
S-
ZXCT1110
LOAD
GND
OUT
OUTPUT
V
OUT
13k
GND
Figure 3. Example Circuit using ZXCT1110
Protection Against Load Short Circuit
In the event of a load short circuit or overload, a large proportion of the supply voltage may appear between the sense
terminals. The supply may be current limited, but there is normally a large reservoir capacitor which can deliver enough
energy to damage the ZXCT11xx before the supply voltage falls to a safe level due to current limit activation.
The ZXCT11xx is rated for a maximum sense voltage of +0.8V, but is safe if the input current is limited to ±8.5mA. In Figure
4, the resistor R
limits the current and therefore protects the current monitor device against load short circuit without
PROT
introducing significant current measurement error.
13 of 16
ZXCT1107/1109/1110
JULY 2011
www.diodes.com
© Diodes Incorporated
Document number: DS35033 Rev. 3 - 2