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audio/videoZONE Products for the week of September 7, 2009
Intersil Says…
ISL99201: Audio Amplifiers Feature Low Power Consumption, High RF Immunity
ISL99201 and ISL99202 Feature Audiophile Quality Performance, Superb Power Efficiency, Click-and-Pop Suppression, Complete Undervoltage and Short Circuit Protection
Intersil Corporation, a world leader in the design and manufacture of high-performance analog and mixed-signal semiconductors, introduced two new audio amplifiers featuring the industry’s lowest power consumption, smallest size, and highest RF immunity.
The ISL99201 and ISL99202 are the first audio products in a new family of ultra-small-footprint packages that will enable smaller, thinner and lighter consumer devices that run longer on a battery charge. These audio amplifiers are particularly well suited for use in SmartPhones, PDAs, game consoles, MP3 and personal media players, personal navigation devices and LCD TVs.
The ISL99201, available in 9-bump 0.4mm pitch WCSP, is the world’s smallest Class D amplifier. It is a filterless, fully integrated, high-efficiency mono amplifier capable of delivering up to 2.5W into a 4 ohm load. It features a low-noise modulation scheme, operating with 86 percent efficiency at 400mW into 8 ohms, and has a signal-to-noise ratio (SNR) that is better than 95dB. The ISL99201 also includes a micropower shutdown mode with a typical shutdown current of 200nA. The fully-differential input of the ISL99201 provides 75dB rejection to common mode noise on the input. The ISL99201 is available in three fixed-gain settings that reduce Bill-of-Materials (BOM) costs and save board space. It is also available with programmable gain setting option for design flexibility. In addition to the WCSP package, the ISL99201 is available in an 8-lead TDFN package.
Available in 12-bump 0.4mm pitch WCSP, Intersil’s ISL99202 is the world’s smallest stereo capfree headphone amplifier, and supports 16 ohm to 600 ohm speaker impedance. Its ultra-wide operating voltage of 2.4V to 5.5V makes the new amplifier ideal for use in mobile battery-powered applications that use 2 AA or single cell Li-Ion batteries, as well as in notebook computers using 3.3V to 5V power supplies. It is also available in 12-lead TQFN package.
EN-Genius Says…
The ISL99201 mono Class-D speaker amplifier does appear to be the smallest Class-D amplifier out there in its WCSP format.
The input is differential and the output uses a bridge-tied load. There is an on-chip spread spectrum sawtooth generator (with an average frequency of typically 375 kHz) for the modulation of the audio signal (two phases, 180º apart) using comparators for production of the digital signal. Both the positive and negative gate drivers have slew rate control reducing the EMI even further below that caused by the spread spectrum technique. The two pairs of power MOSFETs are on-chip, as are the bias and reference generation.
As has become a marketing habit among contenders for Class-D sales volume the product is claimed to not require output filters. Unless the speaker leads are extremely short that is not a likely practical scenario.
The DFN version of the part has an additional pin for the use of external synchronization, if required, which can be from 250 kHz to 800 kHz. (Although the CSP version has an additional “pin” analog power and ground are connected separately from digital.)
The power ratings of the ISL99201 at 10% THD are 1.4 W at 1 kHz into 8 Ω with a 5.0 V rail (the front page of the data sheet states this power gives a THD of 1%), falling to 0.75 W with a 3.6 V rail. In the former case efficiency is a typical 90%. PSRR, which Intersil claims to be protection against 217 Hz interference from GSM phones (I would argue that is rather specious) is a typical 65 dB (not a negative number, Intersil) and that falls off quite rapidly with lower than 5 V rails.
Gains in the ISL99201 can be bought by version. A, B, and C versions offer nominal 6 dB, 9.6 dB, and 12 dB gains, respectively with input resistances (not impedance, Intersil) of 70 kΩ, 46.25 kΩ, and 35 kΩ. There is also a D version on offer that can be gain set with an external resistor.
Although the version of the data sheet currently offered is dated February 27, 2009 (for an August 2009 News Release) there are too many misquotes plus text lifted from other products (“each channel,” for example) and Intersil needs to get its data sheet QA for this product, at least, up to a new level.
The ISL99202 is an output capacitor-free stereo headphone amplifier with a perfectly adequate 63 mW typical output at 1 kHz with a 5 V rail, a THD of 1%, and into a 32 Ω load.
The clever thing about the ISL99202 is that instead of providing an always-on – and therefore power consuming – charge pump to provide an output centered around ground, they have used a negative voltage regulator that dynamically changes voltage according to audio demand levels. Intersil also claims an input circuit architecture that is less immune to demodulating 217 Hz TDM, although there are no numbers about the degree of immunity in the data sheet.
The part has click and pop suppression, and the bias and reference circuits are on chip. There is also short-circuit and undervoltage protection, and thermal shutdown. Power shutdown is provided on an external pin. The supply voltage range is from 2.4 V to 5.5 V with a quiescent of typically 3 mA (at 5 V) and a shutdown current of 100 nA.
The ISL99202 can drive loads from 16 Ω to 600 Ω and the voltage gain is a typical -1.50 V/V with a channel balance of typically ±0.15%. SNRs exceed 100 dB and crosstalk between channels is a typical -76 dB.
Both the ISL99201 and ISL99202 will sell in huge quantities and, although already aggressively priced, the street pricing will probably be half of the 1000-piece pricing noted here. The size of both parts in WCSP and WLCSP, respectively, can demand a premium and the lower power consumption of the headphone amplifier with the dynamic negative voltage regulator will also win design hearts. If that system works as advertised there is no reason we should not see a Class-F amplifier from Intersil quite soon.
The ISL99201 is in production TDFN-8 and WCSP-9 priced at $0.56 and $0.47, respectively, in 1000-piece lots. The ISL99202 is sampling in TQFN-12 and WLCSP-12 and will be priced at $0.72 and $0.65, respectively, also in 1000-piece lots.
Data Sheet ISL99201
Data Sheet ISL99202
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