WT9110B Audio Amplifier IC
28W Class‑D · 6–14.5V · >90% Efficiency · Differential Input · ESOP‑8
The WT9110B is a high‑power mono Class‑D audio amplifier designed for premium portable and smart audio applications. It delivers 28W into a 4Ω load at 14.5V (THD+N ≤ 10%) and offers >90% efficiency, eliminating the need for heatsinks in most designs. The device operates over a wide 6–14.5V supply range and features a differential input structure for excellent noise rejection. An integrated CTRL pin combines mode selection and shutdown, simplifying system control. The filter‑free architecture reduces external components, while built‑in feedback resistors allow for flexible gain adjustment. Housed in a thermally‑enhanced ESOP‑8 package, the WT9110B includes comprehensive over‑temperature and short‑circuit protection, making it ideal for Bluetooth speakers, smart speakers, navigation devices, and portable audio systems.
- 28W output @ 14.5V, 4Ω (THD+N ≤ 10%)
- >90% efficiency – no heatsink required
- 6–14.5V wide supply range
- Differential input – excellent noise immunity
- Integrated CTRL – enable and mode control
- ESOP‑8 package with thermal pad
WT9110B Key Features
WT9110B Electrical Specifications (TA = 25°C)
| Parameter | Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply Voltage | — | 6.0 | — | 14.5 | V |
| Quiescent Current | VDD=9V, no load | — | 10 | 17 | mA |
| Efficiency | — | — | 90 | — | % |
| Output Power (4Ω) | VDD=14.5V, THD+N≤10% | — | 28 | — | W |
| Output Power (4Ω) | VDD=12V, THD+N≤10% | — | 20 | — | W |
| Output Power (4Ω) | VDD=9V, THD+N≤10% | — | 11.5 | — | W |
| Output Power (8Ω) | VDD=14V, THD+N≤10% | — | 14 | — | W |
| Gain | RIN=27kΩ | — | 25 | — | dB |
| Oscillator Frequency | — | — | 520 | — | kHz |
| Output Offset Voltage | VIN=0V | — | 10 | — | mV |
| Thermal Shutdown | — | — | 180 | — | °C |
| Start‑up Time | Bypass=1µF, VDD=9V | — | 240 | — | ms |
Gain can be adjusted using external RIN. AV = 580kΩ / (RIN + 5kΩ).
Pin Description – ESOP‑8
| Pin | Name | Function |
|---|---|---|
| 1 | CTRL | Enable and mode control (high = active, low = shutdown). Do not float. |
| 2 | BYP | Internal common‑mode reference – connect 1µF capacitor to GND |
| 3 | INP | Non‑inverting input (differential) |
| 4 | INN | Inverting input (differential) |
| 5 | VON | Negative output (BTL) |
| 6 | VDD | Power supply (6–14.5V) |
| 7 | GND | Ground |
| 8 | VOP | Positive output (BTL) |
| 0 (Pad) | E‑GND | Exposed thermal pad – must be soldered to GND with large copper area |
The CTRL pin combines mode selection and shutdown. A single pin controls both functions, saving GPIO on the host MCU.
Control & Mode Selection
The CTRL pin provides integrated control for both mode selection and shutdown:
| CTRL Voltage | Chip Status |
|---|---|
| < 0.5V | Shutdown – low power consumption |
| 1.9V – 5V | Active (D Class) – normal operation |
The CTRL pin must be driven to a valid logic level and not left floating.
WT9110B Gain Setting
The gain is set by an external resistor RIN using the following formula:
- With RIN = 27kΩ, gain ≈ 25dB
- With RIN = 43kΩ, gain ≈ 21.6dB
- The input capacitor (CIN) and RIN form a high‑pass filter: fC = 1 / (2π × (RIN + 5k) × CIN)
The BYPASS capacitor (pin 2) is critical – a 1µF capacitor is recommended for optimal pop suppression and PSRR.
Protection & Safety
- Over‑Temperature Protection (OTP): Shuts down output when junction temperature exceeds ~180°C.
- Short‑Circuit Protection (SCP): Protects against output short to ground or supply.
- Under‑Voltage Protection: Prevents operation below safe voltage levels.
Design & Layout Recommendations
- Thermal management: The exposed pad must be soldered to a large ground plane with multiple vias (1mm spacing) for heat dissipation.
- Decoupling: Place 10µF and 0.1µF capacitors as close as possible to the VDD pin.
- Input configuration: For differential input, connect INP and INN to the source. For single‑ended, connect INN to ground via a capacitor and apply signal to INP.
- Output traces: Keep traces to the speaker short and ≥1mm wide.
- RC snubber: For low‑impedance loads, add a 2–5Ω resistor + 500pF–10nF capacitor across the output to absorb voltage spikes.
- EMI: For long output traces or sensitive devices, use an LC filter (33µH, 2.8A + 102–105 capacitor) close to the IC.
For EMC compliance, add an LC π‑filter (10–22µH, 2.8A) on the supply line and separate analog/digital grounds with a 0Ω resistor or ferrite bead.
WT9110B Applications
Why Choose WT9110B
FAQs
What is the WT9110B?
A high‑power mono Class‑D amplifier delivering 28W at 14.5V/4Ω with >90% efficiency and an integrated CTRL pin.
What is the supply voltage range?
6V to 14.5V, supporting a wide range of power sources.
What is the output power?
28W into 4Ω at 14.5V (THD+N ≤ 10%), or 20W at 12V.
How do I enable or disable the chip?
Drive the CTRL pin high (>1.9V) for active mode, or low (<0.5V) for shutdown.
Does it need an output filter?
No – the filter‑free design eliminates the need for external filtering components.
Can I adjust the gain?
Yes, gain is set by an external resistor RIN: AV = 580kΩ / (RIN + 5kΩ).
What is the package type?
ESOP‑8 with an exposed thermal pad for heat dissipation.
What protection features are included?
Over‑temperature protection (OTP) and short‑circuit protection (SCP).
Note: For FM radio applications, the WT9110B’s Class‑D design is optimized for low EMI. The exposed pad must be soldered to a large ground plane for optimal thermal performance. When testing, use an AUX‑0025 filter and add a 33µH inductor in series with the load to simulate speaker impedance. Refer to the datasheet for complete application guidelines and PCB layout recommendations.
