HOW TO CHECK 3V_5V(RT8206b) SYSTEM ON LAPTOP MOTHERBOARD

HOW TO CHECK 3V_5V(RT8206b) SYSTEM ON LAPTOP MOTHERBOARD

Laptop Motherboard need 3V and 5V power system. This 3V_ALW supply VSB (voltage switch button)-EC Bios IC-EC (embedded controller)-SB(South bridge) and more other important component .5V suplay power Source for any switching transistor and device .(USB-HDD-Optical etc).

Without this 3V and 5V Power circuit board will totally death.

RT8206A/B dual step-down, switch-mode powersupply (SMPS) controller generates logic-supply voltages in battery-powered systems. The RT8206A/B includes two pulse-width modulation (PWM) controllers fixed at 5V/3.3V or adjustable from 2V to 5.5V. An optional external charge pump can be monitored through SECFB(RT8206A).

This device also features a linear regulator providing a fixed 5V output. The linear regulator provides

up to 70mA output current with automatic linear-regulator bootstrapping to the BYP(pin 9)switchover source voltage input for the LDO. .

The RT8206A/B includes on-board power-up sequencing, the power-good outputs, internal soft-start, and internal soft-discharge output that prevents negative voltages on shutdown.

Checking this IC need to know how they work and knowing important input and output Voltage :

INPUT POWER

1.VIN (Pin 6) 6v-25V

Power-supply Input.This input value between 6V to 25V according adapter or battery usage and ADP+power source. VIN is used for the constant on-time PWM one shot circuits. VIN is also used to power the linear regulators. The linear regulators are powered by SMPS1 if VOUT1 is set greater than 4.66V and BYP is tied to VOUT1.

2.ENLDO (Pin 4) 6V-15V

LDO Enable Input. The REF/LDO is enabled if ENLDO is within logic high level and disable if ENLDO is less than the logic low level.This power input between 6V to 15V ,some of other circuit manufacture powered VIN or B+ and the other using diode .

After VIN and ONLDO power present LDO(pin 7) will having output for 5V than supply VL(Voltage Linear) to activate EN1(pin 14) and En2(pin 27).

EN1 is SMPS1 input enable than SMPS output will trigger Upper n channel gate trough UGATE1(pin 15) for 5V . 

EN2 is SMPS2 input enable for UGATE2 than SMPS output will trigger Upper n channel gate trough UGATE1(pin 15) for 5V .High-Side MOSFET Floating Gate-Driver Output for SMPS1. and swings between PHASE1/2 and BOOT1/2. 

PVCC (pin 19) PVCC is the supply voltage for the low-side MOSFET driver LGATEx. Connect a 5V power source to the PVCC pin (bypass with 1uF MLCC capacitor to PGND if necessary). There is an internal 10Ω connecting from PVCC to VCC. Make sure that both VCC and PVCC are bypassed with 1uF MLCC capacitors.PVCC input coming from VL .if LDO no voltage present than PVCC will not triger Lower n channel mosfet.VCC (pin3) is analog suplay input voltage for PWM core.with out this power SMPS will not activated .Be ware also PGND need for SMPS power ground..

If VIN present 6-25V and ONLDO present 6 to 15V but LDO not present .check feedback on pin 7 LDO.if there is no feedback positively RT8206B damage.

If VIN present 6-25V and ONLDO present 6 to 15V and LDO present for 5V positively RT 8206B on good condition .Make sure LDO continuity to VL and triger EN1 and activated SMPS1.SMPS2 will activated after SMPS1 activated and become gate driver for both upper n channel 3V and 5V.

If all power above available but Ugate1 and 2 doesn't comes out check FB1 SMPS1 Feedback Input. Connect FB1 to VCC or GND for fixed 5V operation. Connect FB1 to a resistive voltage divider

from VOUT1 to GND to adjust output from 2V to 5.5V.and do same way for FB 2 to adjust output from 2V to 3.3V.

Link Ref : http://adiedkhazbook.blogspot.co.id/p/how-to-check-3v5vrt8206b-system-on.html