The LM4990 is an audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 1.25 watts of continuous average power to an 8Ω BTL load and 2 watts of continuous average power (LD and MH only) to a 4Ω BTL load with less than 1% distortion (THD+N+N) from a 5VDC power supply. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4990 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement.
Circuit Diagram :
The LM4990 features a low-power consumption shutdown mode. To facilitate this, Shutdown may be enabled by either logic high or low depending on mode selection. Driving the shutdown mode pin either high or low enables the shutdown pin to be driven in a likewise manner to enable shutdown. The LM4990 contains advanced pop & click circuitry which eliminates noise which would otherwise occur during turn-on and turn-off transitions. The LM4990 is unity-gain stable and can be configured by external gain-setting resistors.
FeaturesUser selectable shutdown High or Low logic Level
Key Specification
| Improved PSRR at 217Hz & 1KHz | 62dB |
| Power Output at 5.0V, 1% THD+N, 4Ω (LD and MH only) | 2W (typ) |
| Power Output at 5.0V, 1% THD+N, 8Ω | 1.25W (typ) |
| Power Output at 3.0V, 1% THD+N, 4Ω | 600mW (typ) |
| Power Output at 3.0V, 1% THD+N, 8Ω | 425mW (typ) |
| Shutdown Current | 0.1µA (typ) |
Applications
- Mobile Phones
- PDAs
- Portable electronic devices
Source: www.national.com
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