iC-JJ
POWER MANAGEMENT IC
Rev A1, Page 14/17
DESCRIPTION OF FUNCTIONS
BOOST CONVERTER
If VA1x is connected to ground, a voltage of 30V becomes available at VA1. An external voltage divider can be
used to adjust voltages at VA1 from VBAT+2V to +48V. In this case the band gap voltage of 2.44V is present
VA1
R1
VA1x
R2
Figure 1: Adjustment V(VA1)
at VA1x. The voltage at VA1 can be calculated via VA1= 2.44V ( (R1+R2)/R2).
AUTARKY / LOW VOLTAGE DETECTION
To create a system with a redundant voltage supply, measurement inputs VM and VMR are connected to KL15
and KL15R respectively via a 511S resistor. If both supply inputs are used they need to be connected with 511S
to VBAT. If only one of the two inputs (VM or VMR) is used the unused inputs must be connected to GND.
The system is checked for low voltage and autarky via the internal voltage dividers (at 100kS each). The voltage
dividers are shut off in standby mode. The outputs of the two comparators for low voltage and autarky are AND-
gated, meaning that a message at VTU or NVTA delayed by one clock pulse (8us) is only generated when the
relevant voltage thresholds are undershot at both measurement inputs. A reset of the outputs VTU and/or NVTA
via the microcontroller with a rising edge at VTU is only possible if low voltage or autarky is no longer detected.
AUTARKY CIRCUIT / MEASUREMENT OF AUTARKY CAPACITANCE
The switch between VA and VB is closed for at least 5 clock cycles after autarky has been detected. With this,
the voltage of the autarky capacitor is connected to the input of the VA1 up converter; a stable VA1 voltage can
thus be maintained during autarky. At the same time the 30mA current source, which supplies current for
charging the autarky capacitor, is switched off.
The voltage of the autarky capacitor can be measured at output VVA (V(VVA)= 1/8 V(VA). This serves to check
whether the capacitor is charged to a suitably high voltage to sustain the system during autarky. The capacitance
of the capacitor can be determined while the capacitor is being charged. The system’s energy consumption can
be determined during autarky.
Autarky can be simulated using NVTA as an input. If V(VA) > 21V, then the switch between VA and VB can be
closed via a rising edge at NVTA. The 30mA current source is then shut down and the autarky capacitor is
discharged to the level of the threshold voltage (V(VA)= 21V). This is automatically followed by the switch being
opened and the current source switched on again. A second falling edge at NVTA will stop discharging the
capacitor if V (VA) >21V.
ICHAUS [ IC-HAUS GMBH ]
