2 — INSTALLATION AND WIRING
Curtis 1239E-1269E Manual, os 37.0 RevA – May 2021
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pg. 18
KSI and Coil Return
The KSI input provides positive voltage for the low power control circuit. This includes the
microprocessors, power supply outputs, and power for the digital and PWM outputs.
Coil Return (pin 13) should be wired to the positive 12V battery/power source side of the contactors
being driven so that switching noise associated with PWM operation of the contactors is localized
to the contactor wiring only (see Figures 5 & 6).
It is important to maintain the division between KSI and coil return in order to ensure reverse
polarity protection (e.g., vehicle wiring correct, 12V battery/power source terminals reversed).
KSI and COIL RETURN INPUT SPECIFICATIONS
Name Pin
Operating
Voltage
Input Current Protected Voltage ESD Tolerance
KSI 1
8V to 20V
13 A max * continuous ± 20V
± 8 kV (direct
strike)
Coil Return 13 12A
(KSI – 0.3V) to 20V
* Including current from the coil return (pin 13).
Do not connect KSI or Coil Return to the high‑voltage (B+) traction battery.
Throttle and Brake Inputs
e two pot inputs are independently programmable to allow use of a voltage throttle or a 2-wire or
3-wire resistance throttle. Voltage throttles require only the Pot Wiper input (with low power ground
for the return line). Resistance throttles require Pot Wiper and Pot Low (2-wire) or Pot High, Pot
Wiper, and Pot Low (3-wire). All throttle I/O is protected against shorts to KSI or low power ground.
Alternatively, these two inputs can be used for analog signals other than the throttle and brake pot
inputs. Conguring the inputs for use with other signals requires VCL programming; see Chapter 10.
THROTTLE INPUT SPECIFICATIONS
Name Pin
Operating
Voltage
Input
Impedance
Current
Protected
Voltage
ESD
Tolerance
Throttle Pot High 15
0V (shorted to
Pot Low) 5V
(open circuit)
N/A 1 mA nominal (source)
–0.5V to 20V
± 8 kV
(direct
strike)
Pot2 High 27
Throttle Pot Wiper 16
0 to 6.25V
100 kΩ min
(voltage and
3-wire)
0.76 mA nominal
(source, 2-wire)
Pot2 Wiper 17
Pot Low 18 0 to 0.25V 20 Ω nom.
Faults if above 15 mA
(sink)
–1V to 20V
13
24
1
23
35
12
Quick Links:
Figures 5 & 6 wiring
diagram p.12-13
rottle & Brake Types p.22
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