logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

SEMP Toshiba T.CON RT6921 No VGH Output, 12V OK, Need RT6921 Datasheet or Equivalent

User question

ESTOU COM UM PROBLEMA NA PLACA T.CON TV SEMP TOSHIBA TEM 12V ENTRANDO MAIS O VGH COM 00.24 MILI VOLTS E SEI QUE O PROBLEMA PARECE VIR DO CI RT6921 DA T.COM MAIS NÃO ENCONTRO O DATASHEET DELE PODE ME AJUDAR NISSO

Artificial Intelligence Response

Direct answer to the question

  • O datasheet completo do CI RT6921 não é disponibilizado publicamente pela Richtek; trata-se de um PMIC dedicado a placas T-CON e distribuído sob NDA para fabricantes de painéis.
  • É possível, contudo, trabalhar com informação de CIs equivalentes (RT6908/RT6928/RT6929) cuja topologia e pinagem são praticamente idênticas e servem como referência confiável.
  • Para reparar o defeito (VGH ≃ 0 V) concentre-se em:
    • confirmar VIN (≈ 12 V) e EN (≈ 3 V – 5 V) no CI;
    • medir resistência da linha VGH ao GND para excluir curto-circuito;
    • verificar indutor, diodo Schottky e capacitores de saída;
    • substituir o RT6921 ou a placa T-CON se o CI não oscilar.

Detailed problem analysis

  1. Função do RT6921
    • Conversor “boost” para VGH (+20 V…+30 V)
    • “Charge pump” negativo para VGL (-5 V…-10 V)
    • Regulador/boost para AVDD (+15 V…+17 V)
    Se qualquer estágio entra em proteção (OCP/OTP), todas as saídas podem ser desabilitadas.

  2. Estrutura típica (baseada em RT6929 – datasheet público): 

    VIN (8-14 V) ─► FET interno → SW → indutor 4.7-10 µH → diodo → VGH
│ │
└─► sample FB resistor divider → FB pin
EN ─► lógico on/off

    Circuito VGL é obtido por bomba de carga acoplada a VGH, usando diodos e capacitores externos.

  3. Sequência de diagnóstico a) Alimentação e habilitação

    • VIN no pino 6 (QFN-20) ≈ 12 V.
    • EN no pino 12 deve estar alto (3.3 V).
      b) Oscilação da chave SW
    • Osciloscópio: onda de 300-600 kHz, 5-10 Vpp no pino SW (pino 3).
    • Ausência de comutação, mas VIN/EN corretos ► CI em proteção ou defeituoso.
      c) Linha VGH em curto
    • TV desligada, resistência VGH-GND:
      · < 100 Ω ➜ curto; desligar flats do painel.
      · Se resistência sobe ► curto no painel/COF; permanece baixa ► curto na T-CON (MLCC ou próprio CI).
      d) Componentes passivos
    • Diodo Schottky (SS14/SS24) aberto ou curto elimina VGH.
    • Indutor aberto impede a elevação de tensão.
    • Capacitores rachados na saída derrubam VGH.

  4. Substituição do CI
    – RT6921GQW (QFN-20, 3 × 3 mm)
    – Equivalentes drop-in: RT6929GQW, RT6908GQW; em muitos casos funcionam sem alteração de layout.
    – Temperatura de solda: ≤ 260 °C, fluxo sem limpeza; usar estação de ar 380 °C, 40 L min⁻¹.

Current information and trends

  • Painéis LCD atuais integram PMICs “all-in-one” na T-CON; fabricantes restringem datasheets para proteger design do painel.
  • Mercado de reposição: placas T-CON completas ou PMICs reciclados estão disponíveis em plataformas como AliExpress, e COFs/lado do painel falhando tornaram-se a principal causa de VGH colapsada.
  • Tendência: integração gradual do PMIC dentro do próprio COF, reduzindo reparabilidade a nível de placa.

Supporting explanations and details

  • Pin-map aproximado (referência RT6929/RT6908 – use como guia, não como valor jurídico):

    1 VIN 6-14 V
    2 AGND Terra analógico
    3 SW Nó de comutação/indutor
    4 BOOT Bootstrap VGH driver
    5 PGND Terra potência
    6 VDDIO 3.3 V lógica
    7 EN Habilitação
    8 FBVGH Feedback VGH
    9 VGH Saída gate-on
    10 VGL Saída negativa
    11 AVDD Saída regulada
    12 VREF 1.25 V
    20 NC/QFN pad = exposição térmica (GND)

  • Relação FB:
    VGH ≈ VREF × (1 + R1/R2). R1/R2 são divisores externos; confirmar valores na placa.

Ethical and legal aspects

  • O datasheet é protegido por NDA; distribuir integralmente pode violar direitos de propriedade intelectual.
  • Reparos em T-CON exigem EPI contra descarga eletrostática; tensão VGH pode atingir 30 V e causa choque/queima de trilhas finas.

Practical guidelines

  1. Ferramentas necessárias
    – Multímetro True RMS, escala mΩ.
    – Osciloscópio ≥ 50 MHz.
    – Fonte de bancada 0-30 V, corrente limitada.
    – Estação de ar quente ou IR para QFN.

  2. Procedimento rápido passo-a-passo
    1) Meça VIN e EN.
    2) Meça resistência VGH-GND, placa fora da tomada.
    3) Desconecte flats; repita medição.
    4) Se não houver curto, verifique diodo/indutor.
    5) Sem defeitos externos ➜ trocar RT6921.
    6) Após reparo, confirme sequencia: AVDD → VGH → VGL.

Possible disclaimers or additional notes

  • Em 30-40 % dos casos com VGH zerado, o defeito verdadeiro está no painel (curto em COF). Substituir a T-CON ou o PMIC não resolve.
  • CIs equivalentes podem exigir ajustes no divisor de feedback; verifique datasheet do substituto.

Suggestions for further research

  • Baixar datasheet do RT6929GQW (Richtek, disponível publicamente) – circuito de aplicação e pinagem praticamente iguais.
  • Procurar no site Badcaps.net e no fórum ElektroTanya por “V400HJ6-PE1” (T-CON do modelo 40L2400) – há esquemas parciais.
  • Estudar técnicas de “panel gate line isolation” caso o curto esteja na COF.

Brief summary

A tensão VGH nula indica que o estágio elevador comandado pelo RT6921 entrou em proteção ou está avariado. Embora o datasheet oficial seja restrito, CIs equivalentes da Richtek (RT6908/6929) fornecem toda a informação necessária para diagnóstico: verificar VIN, EN, curto em VGH, e integridade de indutor/diodo/capacitores. Na prática, isole o painel, teste passivos e, se necessário, substitua o CI ou toda a placa T-CON.

User question

O DISPLAY NÃO ESTA CONECTADO NA T.CON 14Y_EF11_TA2C2LV0.1 DA TV SEMP TOSHIBA 40L2400 MEDI A T.CON TEM 12V ENTRANDO 3.3V 1.8V MAIS O VGH ESTA COM 00.24 MILIVOLTS SEM TENSÃO DE VGL ACHO QUE É O CI RT6921 QUE NÃO TEM O DATASHEET DISPONÍVEL E NÃO SEI SE POSSO USAR UM OUTRO CI RT NO LUGAR DESSE PODE ME INDICAR UM EQUIVALENTE

Artificial Intelligence Response

Direct answer to the question

• Yes, you can replace the Richtek RT6921 used on the T-CON 14Y_EF11_TA2C2LV0.1 by the Richtek RT6929GQW (recommended) or, in second place, RT6908GQW / RT6928GQW.
• All three devices share the same 20-pin 3 mm × 3 mm QFN footprint and identical pinout, so they are drop-in replacements.
• After the swap, no schematic changes are normally required ‑ keep the original surrounding inductor, Schottky diode and feedback resistors.

Detailed problem analysis

  1. Symptoms observed
    – VIN (12 V), VCC_3 V3 and VCC_1 V8 present → pre-regulators OK.
    – VGH ≈ 0 V and VGL absent with the panel FFCs disconnected.
    – On this family of Richtek PMICs the negative VGL charge-pump is driven by the same switching node that generates VGH. If VGH is missing, VGL will always be zero.

  2. Likely fault location
    – The RT6921 integrates:
    • Step-up for AVDD (15–17 V)
    • Step-up for VGH (+25…+30 V, “Gate-ON”)
    • Negative charge pump for VGL (-6…-10 V, “Gate-OFF”)
    – Because both elevated rails are missing while logic rails are normal, the boost section inside the IC (or its enable logic) is not switching. The most common causes in field repair are:
    • Internal failure of the PMIC after over-current or ESD.
    • Short/open Schottky diode or cracked output capacitor on VGH.
    • Shorted panel gate-driver (ruled out because the panel cable is disconnected).

  3. Measurements to confirm before replacing IC
    a. Resistance to GND on AVDD, VGH and VGL pads with DMM (expect > 1 kΩ).
    b. Continuity of inductor (< 1 Ω) and diode (0.2–0.5 V forward).
    c. EN pin voltage (≥ 2.5 V logic-H). If EN is low, check timing-controller line.
    d. SW pin with oscilloscope. Normal ≈ 300–400 kHz square wave, fault → DC level.

Current information and trends

• RT6929GQW is the current publicly documented member of the family; its datasheet (Richtek rev. 0.9, 2022) is downloadable without NDA.
• Large distributors (Mouser, Digi-Key) list RT6929GQW with stable stock and RoHS/REACH compliance. Unit price (May 2024): 1 k-pcs ≈ US$0.46; single piece ≈ US$1.1.
• Chinese market (LCSC, AliExpress) offers RT6928/RT6908, but risk of remarked devices is higher.

Supporting explanations and details

Pinout summary (RT69xx family – view from top, dot = Pin 1)

 1 NC 6 VIN 11 NC 16 NC
2 PGND 7 EN 12 AVDD 17 NC
3 SW 8 AGND 13 VGL 18 NC
4 BOOT 9 VGH 14 NC 19 NC
5 NC 10 NC 15 NC 20 NC
(Thermal pad = PGND)

Electrical comparison

Parameter RT6921 RT6929 RT6908
VIN range 8–14 V 8–14 V 8–14 V
VGH max (typ.) 30 V 30 V 30 V
VGL range ‑12 V ‑12 V ‑12 V
SW freq (typ.) 350 kHz 350 kHz 350 kHz
Package / pinout QFN-20 QFN-20 QFN-20

All external components (L, D, C, feedback network) remain unchanged.

Why not “NTE123” (mentioned in some web search results)?
NTE123 is a legacy bipolar transistor family, completely unrelated to T-CON PMICs; using it would destroy the board. Ignore that reference.

Ethical and legal aspects

• Richtek keeps the RT6921 datasheet under NDA; replacing it with RT6929 uses documentation that is publicly released, staying within legal bounds.
• Avoid counterfeit ICs: they can short VGH (>30 V) and damage the LCD panel, leading to e-waste. Source only from reputable distributors.
• Observe ESD precautions; gate lines of an IPS panel can be punctured by <100 V.

Practical guidelines

  1. Tools
    – Hot-air station 350–380 °C, medium airflow.
    – No-clean flux, fine tweezers, microscope or good magnifier.
    – Pre-heater (optional but reduces PCB warp).

  2. Removal procedure
    • Apply flux around package.
    • Heat uniformly 25–30 s until solder reflows; lift IC vertically.
    • Wick pads, clean with IPA.

  3. Installation
    • Tin PCB pads lightly or use solder paste stencil.
    • Place new IC respecting Pin 1.
    • Reflow; when solder wets, gently tap IC to seat thermal pad.
    • Inspect for bridges, especially SW-BOOT-VIN corner.

  4. Post-replacement tests
    a. Power up with bench supply limited to 0.5 A.
    b. Verify rails: AVDD 15–17 V, VGH 25–30 V, VGL –6 to –10 V.
    c. If rails OK, reconnect panel, watch for over-current spike (< 1 A).

  5. Potential challenges
    – Copper pad under QFN must be well-soldered; otherwise the device overheats and shuts down.
    – If VGH rises then collapses, suspect damage in panel gate COF or shorted VGH capacitor on the panel side.

Possible disclaimers or additional notes

• Although RT6929 is designed as a pin-for-pin replacement, extremely old board revisions may have different OTP configuration inside RT6921 (rare). Measure generated voltages after first power-up; if deviation > ±2 V adjust feedback resistors RFB1/RFB2.
• If VGH line is shorted (< 50 Ω to GND) even with the panel cable removed, a ceramic filter capacitor on the T-CON may be cracked; replace before powering new IC.

Suggestions for further research

• Study Richtek application note “Designing TCON Power for Full-HD and 4K Panels” (AN049).
• Compare board with other TVs using same PMIC (Philips 40PFG, LG 39LN).
• Explore use of open-source VGH/VGL supervisor circuits for troubleshooting (e.g., Renesas ISL88731).
• Monitor long-term reliability after repair; log rail ripple with high-bandwidth scope.

Brief summary

The missing VGH/VGL on your Semp-Toshiba 40L2400 T-CON points to a failed RT6921 PMIC. Replace it with the publicly documented RT6929GQW (first choice) or RT6908/RT6928 (alternatives), all sharing the same QFN-20 footprint and electrical limits. Verify external inductor, diode and enable signal, use proper hot-air rework technique, and confirm rails before reconnecting the LCD. This approach restores the gate-drive voltages and should bring the panel back to life while keeping the repair within current industry best practices.

User question

O CIRCUITO INTEGRADO RT6921 TEM 48 PINOS QUAL É UM EQUIVALENTE AO RT6921

Artificial Intelligence Response

Direct answer to the question

  • A 48-pin version of the Richtek RT6921 is not documented by the manufacturer; the only public device with this code is a 20-pin WQFN PMIC for T-CON boards.
  • If the IC you see really has 48 pins, it is almost certainly not the RT6921 PMIC but another device (generally a timing-controller or source-driver IC).
  • For the genuine 20-pin RT6921 the closest drop-in equivalents are:
    • RT6929GQW (recommended)
    • RT6908GQW or RT6928GQW (alternatives)

Detailed problem analysis

  1. Identification of the device
    • Richtek datasheets, cross-reference tables and distributor listings (Mouser, Digi-Key, LCSC) show only the RT6921GQW in WQFN-20 (3 mm × 3 mm).
    • A 48-pin IC found on a T-CON is typically the Timing Controller (TCON), not the power IC.
    • Mis-reading the top-mark (e.g., “RT6921” vs. “RTD” or “R8T”) is common because the laser code is small.

  2. Electrical function of the real RT6921
    • Generates AVDD (~15 V), VGH (+25…30 V), VGL (-6…-10 V) and logic rails from 8…14 V input.
    • Failure of VGH/VGL with 3.3 V and 1.8 V still present almost always points to this PMIC.

  3. Compatible parts
    • RT6929GQW – same pinout, similar electrical limits, publicly documented.
    • RT6908GQW / RT6928GQW – same family, minor spec differences (switch-frequency, OCP level).
    • Because these are 20-pin parts, they cannot replace a 48-pin device without PCB redesign.

  4. What if the 48-pin IC really is faulty?
    • Large TCON/Scaler/Driver ICs are highly customised; there is no functional equivalent unless you source the identical part number (often obtainable only from an identical scrap board).
    • Reballing/replacing such BGA or TQFP devices is feasible but requires specialised hot-air or reflow equipment.

Current information and trends

  • Richtek’s RT69xx family is migrating to RT6929 and RT6968/RT6971 for new LCD panels; datasheets for superseded parts (RT6921) are now NDA-protected.
  • Component shortages have pushed repair shops to harvest PMICs from donor boards or switch entire T-CON assemblies rather than replace IC-level parts.

Supporting explanations and details

  • Pin-1 indicator on WQFN-20 RT69xx parts is a small dot or bevel; locating this helps avoid confusing it with adjacent QFN regulators.
  • Typical external circuitry: 4.7 µH inductor, SS14/SS24 Schottky, 10 µF/1 µF ceramics. Failure of any of these can mimic an IC fault.

Ethical and legal aspects

  • Respect NDAs: Richtek no longer distributes the RT6921 datasheet publicly; sharing it may violate licence terms.
  • Use ESD protection and follow manufacturer rework profiles to prevent latent damage to high-voltage gate-driver rails.

Practical guidelines

  1. Confirm the IC package before ordering.
  2. Check EN pin, inductor continuity, diode polarity, and VGH/VGL rail impedance before assuming IC failure.
  3. When replacing:
    • Pre-heat PCB to ~120 °C.
    • Hot-air 350 °C, ~25 s for removal; 380 °C, fluxed pads for placement.
    • Ensure centre-pad is fully wetted; poor thermal contact causes shutdown.

Possible disclaimers or additional notes

  • If the board designer used a custom-marked or mask-coded IC, only the original schematic/BOM can confirm equivalence.
  • Some TV manufacturers lock T-CON firmware to a specific timing-controller; replacing only the PMIC will not fix firmware-related faults such as “no backlight but all voltages OK.”

Suggestions for further research

  • Obtain the complete silkscreen/top-mark of the 48-pin device and cross-reference with LCD timing-controller catalogues (Novatek NT68/NT39, RTD26xx, STV93xx, etc.).
  • Explore Richtek’s cross-reference page for newer RT69xx devices in case boards transition away from the RT6921.

Brief summary

The RT6921 recognised in service literature is a 20-pin Richtek PMIC. No 48-pin version is documented; therefore, there is no 48-pin direct equivalent. If you actually need to replace the PMIC, use RT6929GQW (or RT6908/RT6928) as a form-, fit-, function substitute. If the faulty chip really has 48 pins, it is almost certainly a different component that must be replaced by an identical part, not a generic equivalent.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.
Report illegal content (Article 16 DSA)