ZXCT1030
Voltage output Current Monitor
Com parator
Referring to the block diagram , the current m onitor The open collector output is active low and is asserted
takes the sm all voltage developed across the sense when Vsense x 10 (Vout) > Vcom p_in.
resistor (Vsense) and transfers it from the large
com m on m ode supply voltage to a ground-referenced
signal with a gain of 10. The sense input com m on
m ode range is 2.2V to 20V. In this range, a linear output
voltage is delivered.
It can be connected to any voltage rail up to Vin via a
pull-up resistor. Suggest values for the resistor are in
the range of 10-100k⍀.
In the case where high load currents or a short circuit
occurs, thus reducing the com m on m ode signals (V+,
V-) typically below 2.2V, the com parator will default to
the asserted state. This can elim inate a closed loop
system ‘latch-up’ condition, allowing the controller to
rem ove the applied power.
Reference
The bandgap reference allows the com parator to
com pare the translated Vsense with threshold value
chosen by the user which can be any voltage from 0 to
1.24V, configured by two external resistors which
form s Vcom p_in.
Stability
The output current which can be drawn from the
To ensure stable operation of the ZXCT1030, it is
recom m ended a decoupling capacitor is placed across
the VCC and ground connections. A ceram ic 10F will
be adequate.
com parator reference (I
source) is lim ited to 5µA,
ref
m aking potentiom eters ≥ 250k⍀ suitable for setting a
threshold level. Where a lower potentiom eter resistor
value is used, an additional resistor value should be
inserted between V and V to m aintain sufficient
ref cc
current for the reference. (as shown in figure 1.0).
PIN CONNECTIONS
FIGURE 1.0
External resistor for reference level
MSOP8
V
8
7
6
5
Com p_out
1
2
3
4
cc
Sense-
Sense+
GND
V
out
Vref_out
Com p_in
Pin Na m e
Pin Fu n ct io n
Vcc
S u p p ly vo lta g e
Ne g a tive s e n s e in p u t
Po s itive s e n s e in p u t
Gro u n d
S e n s e -
S e n s e +
GND
The Voltage reference has a m axim um current sink
capability. This m agnitude of current will be influenced
by the value of R1 which is inserted between Vref and
Vcc. The value of current flowing through R1 can be
expressed as:
Co m p _in
Co m p a ra to r in p u t, u s u a lly a
ra tio o f th e re fe re n ce o r o th e r
co n tro l s ig n a l.
Vre f_o u t
Vo u t
Re fe re n ce o u tp u t
I = (Vcc -Vref) / R1
Cu rre n t Mo n ito r o u tp u t
vo lta g e
Co m p _o u t
Op e n co lle cto r co m p a ra to r
o u tp u t
PROVISIONAL ISSUE J - MAY 2004
5
S E M IC O N D U C T O R S
