1. Vcc <14.8 V
The Zener diode chain is OFF and the R
GND
is used to protect the system against a potential internal failure of
the device. Since the typical current consumption of the ICL device is ~ 1.5 mA (the current contribution of the
Zener diode chain is null in this case), in order to have a certain V
GND
, the R
GND
value is:
RGND =
VGND
1.5mA
(4)
1. Vcc > 14.8 V
In this case the Zener diode chain is enabled and the R
GND
is also used to limite the maximum current
consumption of the device, flowing through R
GND
resistor from GND pin to the system ground MGND.
This current consumption is given by the sum of two contributors:
1.
The net current consumption of the RHRPMICL1A (considering the internal Zener diode chain current as
zero)
2.
The current consumption of the Zener diode chain in ON-state
For example, if we want to set the maximum current consumption of the RHRPMICL1A device to 2 mA, the value
of R
GND
is:
RGND =
VCC − 14.8V
2mA
(5)
The RHRPMICL1A can be configured to work also with power Buses with voltage higher than 52 V, by adding the
proper protection components to the application.
Guidelines on this feature are provided in the RHRPMICL1A datasheet.
2.5
Analog telemetry
The analog telemetry circuit gives information about the current flowing across the load. This circuit provides on
the TM pin a source current whose value is instantly proportional to the current flowing from the bus supply line to
the load. The voltage drop (V
TM
) on the external resistor R
TM
connected between the TM pin and MGND, is
proportional to the load current (I
SENSE
) flowing through R
SENSE
, thus performing a current/voltage conversion:
RTM =
VTM
IRTM
=
VTM
ISENSE
*
RTMS
RSENSE
(6)
2.6
Digital telemetry (status telemetry)
The status telemetry circuit gives some information about the device status, which can be retrieved by monitoring
the STS output pin, according to the following table.
Table 3.
Signal on digital telemetry pin
STS pin signal
RHRPMICL1A driver status
HIGH
ON
LOW
OFF
The STS is an open drain pin that can source a 100 μA fixed current; it is typically connected to MGND through
an external resistor R
STS
, setting the desired high logic level value V
H_STS
as follows:
The following picture shows the telemetry signals during the ICL operation.
UM2605
Analog telemetry
UM2605
-
Rev 1
page 4/27