SMARC-sAMX7 User Guide. Rev. 1.9
// 34
6.3.
RTC current consumption
The current consumption of the sAMX7 was tested with following circuit. Jumper was populated to J58 position 1-2.
With an external power supply J37 was feed with voltages from 2.0 V to 3.4 V.
Figure 8: RTC current consumption with an external power supply and voltages from 2.0 V to 3.4 V
The module RTC (RV-8803) can operate down to 1.5 V, the i.MX7 RTC minimum supply voltage is 2.4 V. Due to the
higher current consumption of the i-MX7 RTC this part is not powered with the V_RTC voltage rail per default
(resistor option on the module).
Table 11: Minimum Supply Voltage of the RTC Module
Ambient
temperature
Maximum Current in
V_BAT_R
Minimum voltage for module RTC (RV-8803)
V_BAT_R/V_RTC
-20°C
0.4
µ
A
2.20V/1.76 V
25°C
0.5
µ
A
2.02V/1.69 V
85°C
1.8
µ
A
2.08V/1.71 V
The BAV99 has higher voltage drops as Schottky diodes. Therefore the performance can be increased by changing
D32 with a Schottky diode, e.g. BAS70.
Because the sAMX7 module has a reverse serial protection in the VDD_RTC signal with a diode, no super cap
charging from module side is possible without shorting the diode on the module.
V_BAT
GND
GND
NC
NC
GND
GND
GND
NC
J37
2
1
V_RTC
BT1
3V
CR2032
V_BAT_R
D32
BAV99
SOT23
3
2
1
V_BAT_D
V_5V0_S5
1
2
3
D54
BAV99
SOT23
V_SCAP
1
2
3
D55
BAV99
SOT23
RTC
V_SCAP_RTC
P1
P2
P3
1
2
3
J58
JUMPER
H10
V_BAT_JP
V_
SC
AP
_J
P
U7
2
5
1
3
4
VOUT
GND
CE
V_VIN
NC
NCP4681
GND
NC
R115
1k
1%
0402
R85
221R
1%
0402
21
.5
x8
5.
5V
1
5
C
36
4
C
20
8
10
0n
50
V
04
02
04
02
50
V
10
0n
C
20
9
R153
1k
1%
0402
0402
1%
0R
R442
DNI
D
N
I
R
44
3
0R 1%
04
02
D37
BAV99
SOT23
3
2
1
NC
V_3V3_S5
