User's Manual l MBa8x UM 0100 l © 2021, TQ-Systems GmbH
Page 40
3.15
Power supply
The MBa8x requires a supply voltage between 16 and 26.7 volts, nominal 24 volts. The following protective circuits are provided
for the input voltage V_24V of the MBa8x:
•
Fuse 7 A, slow blow
•
Overvoltage protection (26.7 V … 29.5 V)
•
Filter circuit for RF interference
•
Reverse polarity protection
The voltages (rails) on the mainboard can be divided into three main paths, consisting of two LM25119s and a TPS45335. These
supply the largest loads (TQMa8x, USB supply, display supply with 12 V).
V_24V
(max. 5.7 A)
LM25119
#2
V_3V3
(max. 8 A)
V_5V_MOD
(max. 6 A)
LM25119
#1
V_5V
(max. 6 A)
V_1V8
(max. 1.3 A)
AP7361C
AP7361C
LT3503
TPS54335
V_1V5_MP
CIE
V_2V5_
ETH
V_1V0_
ETH
Buck
Key:
LDO/
Switch
V_12V
(max. 3 A)
FDC6331
V_3V3_
MPCIE
TQ-Modul
V_3V3_
MB
Power-
Rail
optional
connection to
V_1V8
V_1V8_OUT
(max. 0.7 A)
PFET
V_3V3_OUT
(max . 0.24 A)
optional
Figure 27: Block diagram supply
The design also allows power sequencing of all voltage levels used. With the exception of V_3V3 and V_V5_MOD, all voltages are
switched on after the TQMa8x boots. The PMICx_PGOOD signals of the module are linked together on the mainboard by means
of AND gate and together enable the other controllers in sequence step B. This release automatically activates all linear
regulators (V_2V5_ETH, V_1V0_ETH, V_1V1_USB, V_3V3_MPCIE and V_1V5_MPCIE) as well as the DC/DC regulator for V_5V_CAN.
Attention: Voltages at headers
The internal voltages (1.8 V, 12 V, etc.) provided at the MBa8x headers are not additionally protected.
Technically an overload of the fuse is therefore possible. The resulting total current consumption of
the MBa8x should be kept below 7 A in total.
3.16
Cooling concept
The biggest power loss on the motherboard is caused by the voltage regulators. In addition, the module is a heat source that
indirectly affects the mainboard. Depending on the application, further power losses can occur, mainly on additional external
consumers on the starter kit headers, the Mini PCIe slot, etc.
The use of an optional heat sink or heat spreader is provided for evaluating the TQMa8x under high load cases. Three holes are
available on the MBa8x for this purpose. The metallization of the hole has GND potential.
