Technical data
4.20.1 Real Time Clock Backup Supply (VRTC)
Pin Name Direction Function
25 VRTC Input DC supply for real time clock
VRTC provides an input connection to the Wireless CPU® which allows the user to
power the real time clock (RTC) within the GR64 by way of a coin cell or charged
capacitor.
When the Wireless CPU® is powered, an internal LDO regulator provides a 200A
source designed to supply the microprocessor’s RTC block. It is also intended to recondition a
rechargeable coin cell that supplies the RTC Wireless CPU® when the main battery is
removed, or has insufficient energy. Because this LDO is always on, even when the
Wireless CPU® is powered down, it features very low quiescent current. It also offers
reverse current protection, with low leakage, when the coin cell is powering the RTC
block.
The RTC LDO is primarily designed to charge manganese-silicon lithium batteries.
Rechargeable coin cells with different chemical composition may also be charged
provided their charging requirements are consistent with the RTC LDO’s electrical
characteristics. The VRTC output is nominally 1.5 V.
VRTC LDO characteristics:
Parameter Condition Min Typ Max Unit
Output Voltage Tolerance
IOUT = 10 μA
1.35 1.50 1.65 V
μA
Maximum Output Current 200
Short-circuit Current Limit VRTC to GND 0.7 1.6 2.9 mA
Output Resistance
IOUT = 10 μA
75 100 150 ohm
Line Regulation
IOUT = 10 μA
5 mV
μA
Off Reverse Leakage Current 0.1 1
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GR64 Integrators’ Manual
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