NCV1124 ON Semiconductor, NCV1124 Datasheet - Page 6

• Manufacturer Part Number: NCV1124
• Description: Dual Variable−reluctance Sensor Interface IC
• Manufacturer: ON Semiconductor

example given these system requirements:
1. Determine tradeoff between R1 value and power
rating. (use 1/2 watt package)
= 8.0 mA, which is less than the 12 mA limit.)
2. Determine R
3. Determine V
4. Calculate worst case V
case trip voltage will occur when:
which is still less than the 250 mV minimum amplitude of
the input.
V RS(+TRP) + 11mA
Referring to Figure 2, the following will be a design
Set R1 = 15 k. (The clamp current will then be 120/15 k
Set R
Therefore, R
Examination of equation (7) and the spec reveals the worst
V
IN
INP1 = 15 mA
R1 = 14.25 k (5% low)
R
V RS(+)MAX + 16 mA(17.85 k)
Adj
HYS
Adj
R RS + 1.5 kW (u 12 kW is considered open)
F VRS + 10 kHz @ V RS(MIN) + 40 V pk−pk
= 17.85 k (5% High)
Adj
= 16 mA
= 180 mV
as close to R1 + R
(easily meets 250 mV minimum)
V RS(+TRP) + 166 mV typical
Adj
RS(+TRP)
Adj
+ 229 mV
P D +
V RS(MAX) + 120 V pk
V RS(MIN) + 250 mV pk
= 17 k.
* 15mA(14.25 k ) 1.5 k) ) 180 mV
17 k * 11mA(15 k ) 1.5 k) ) 160 m
using equation (7).
120
R1
2
RS(+TRP)
RS
2
t 1 2 W
as possible.
APPLICATION INFORMATION
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NCV1124
6
5. Calculate C1 for low pass filtering
pass filter using R1 and C1 can be used to eliminate high
frequency noise without affecting system performance.
used.
6. Calculate the minimum R
an open circuit. (DIAG = 5.0 V)
and,
IN
R
V
INP1
R1
K
R RS(MAX) +
Since the sensor guarantees 40 V
Therefore, a cut−off frequency, f
Set C1 = 0.047 mF.
Rearranging equation (7) gives
But, V
Using the following as worst case Low and High:
Therefore,
Adj
HYS
I
Adj
Gain Reduction + 0.29 V
R RS +
R RS +
R RS(MIN) + 16.5 k (meets 12 k system spec)
RS
+ 16.5 k
Worst Case Low (R
23.6 mA = 15 mA × 1.57
= 0 during this test, so it drops out.
135 mV ) 23.6 mA
+ 48.4 k
V HYS ) [INP1
* V RS(+TRP)
185 mV ) 10.7 mA
C1 v
135 mV
16.15 k
15.75 k
16 mA
1.57
2pf C R1
20 V
16 mA
1
INP1
6.0mA
RS
RS
+ 0.0145 + *36.7 dB
v 0.07 mF
)
that will be indicated as
K I
16.15 k
Worst Case High (R
pk−pk
10.7 mA = 7.0 mA × 1.53
C
, of 145 Hz could be
17.85 k
R Adj ]
@ 10 kHz, a low
185 mV
17.85 k
14.25 k
* 15.75 k
6.0 mA
1.53
* 14.25 k
* R1
RS
)