this is my first time here. Please be forbearing if i am doing anything wrong. :-) I am developing a solar charger to charge an 48V LIPO battery with a solar module using the LT8490. By now i am testing the (selfmade) board and it is not looking good. :-(
Testresults: The LT8490 seems to work as the status LED is blinking once (0.25s) every 3.5s. The fault LED is off. I tested the fault LED by using a 12V battery and then the fault LED showed an under-voltage fault as expected in the datasheet. The problem is, that the LT8490 is not charging although the status LED suggests stage 1 charging.
I can not measure any clock signal at the CLKOUT-pin.
Here are the facts:
Battery Voltage: 36.97V
SolarPanelVoltage: 35.36V (I am using a power supply for the tests as the solar panels have not arrived yet)
(MPP is supposed at 37V, open circuit is supposed at 48V)
INTVCC = 6.34V
SWEN = 0.72V
IMON_OUT = 0.7V (but there is no current. Actually imon_out is a pwm-signal from 0V-3.3V with a period of 27.4ms and a high-time of 6ms)
IMON_IN = 0.146V (i think this is normal as the imon_in circuit has an measurement offset of 7mV and there is no current flowing)
CSPOUT = 36.97V
CSNOUT = 36.97V
CSPIN = 35.36V
CSNIN = 35.36V
VBAT = 36.97V
VIN = 35.36V
TG1 = 0V
BG1 = 6.34V
TG2 = 0V
BG2 = 0V
FBIR/FBIN = 1.54V
FBOUT/FBOR = 1.2V
BOOST2 = 5.92V
BOOST1 = 5.92V
FBIW = 2.53V
I am using 4 pieces of IPT007N06N FET's.
I am using 2 CMMR1U-02 TR diodes between GATEVCC and BOOST1/2
MODE is tied to an external 3.3V source.
The input feedback network is configured for 60V using the resistor / capacitor values from the datasheet.
The stage 2 voltage limit (Vs2) is set to 48V.
Charge current limit is set by a poti to 4.8A.
Input current is limited to 20A.
TempSense is not used. (11.5k and 10k resistors)
I attached the essential part of the schematic as the hole board contains way more than just this circuit. Please be aware that i canceled some parts from the schematic for the tests. You will know once you take a look at the schematic.
Please help me finding the bug. I am searching for days and cant find it. It is getting really depressing. I think i am making some very basic mistakes because of some misunderstanding. (My English could be much better) Thanks a lot for every helpful comment!