acquisitionZONE Products for the week of August 9, 2004
Microchip Technology Inc., a leading provider of microcontroller and analog semiconductors, announced an innovative analog device for the digital environment. These devices enable a standard two-stage amplifier signal chain to be implemented into an eight-lead package with a power-saving chip select. The internal connection of the two stages enables one operational amplifier to feed into the other making a more compact design.
Microchip's MCP62x5 devices are extended industrial-temperature range (-40 degrees C to 125 degrees C), Rail-to-Rail input/output (I/O), single-ended operational amplifiers. Covering the 2 MHz, 5 MHz and 10 MHz Gain Bandwidth Product (GBWP), these devices allow for the most current flow efficient design by having low supply-current requirements. With a migration path along the GBWP spectrum, designers can optimize the GBWP to be selected for the current flow versus GBWP demand for the application.
These devices are ideal for sensor, automotive, instrumentation, industrial
and battery-operated applications. The MCP6275 has a 2 MHz-gain bandwidth
and operates at 5.5V to 2.0V with a supply current of 165 microamps. Meanwhile,
the MCP6285 has a 5 MHz-gain bandwidth, operates at 5.5V to 2.2V and has
a supply current of 450 microamps. The MCP6295 has a 10 MHz-gain bandwidth,
operates at 5.5V to 2.4V and has a supply current of 1.0 milliamps.
analogZONE Says . . .
These are new parts in the Microchip MCP627x, 628x and 629x families. They share the same amplifiers as others in the series but with different internal electrical connections. In the MCP629x family, for example, there is the single MCP6291, the dual MCP6292, the single MCP6293 (with chip select) and the quad MCP6294, all in a choice of three packages. The MCP6295 is like the dual MCP6292 except that the output from the A amplifier is internally connected to the non-inverting input of the second amplifier, so cascading them. The common output of the A amplifier and the input of the B amplifier are also available at an external pin allowing for compensation and feedback components to be connected, especially for filters.
The cascaded pair are in standard 8-pin packages so that a pin is freed up for a chip select input to put the device into a low power mode.
The rail can be between 2.4 V to 5.5 V. The press release is misleading about the quiescent current as the numbers quoted are per channel. In these cascaded parts both channels are always in use so the quiescents are doubled. Nontheless the power against bandwidth tradeoffs are still very good. In chip-scale-high mode the ground current is a typical -0.7 µA.
As an example, for 2 mA, the MCP6295 gives a GBW product of 10 MHz, a slew rate of 7 V/µs and the unity-gain phase margin is a typical 65°. Input voltage noise density is a typical 8.7 nV/rtHz at 10 kHz, and the equivalent for current is a typical 4 fA/rtHz at 1 kHz. CMRR is about 90 dB out to 1 kHz, falling to about 66 dB at 20 kHz, and the +ve and -ve PSRR are both about 90 dB out to 20 Hz, falling to about 30 dB at 20 kHz.
The inputs are differential stages in parallel offering a span exceeding Vdd by 300 mV and below Vss by 300 mV. Exceeding the supply voltage range causes no phase reversal. The outputs are also rail-to-rail moving within 15 mV of each rail. However, as these are cascaded amplifiers the input range of the second is limited by the output range of the first. It is also important to note in any application that the load of the first amplifier, without any external correction or change, is the input impedance of the second -- typically 10e13 ohms paralleled with 6 pF. Also, these are voltage feedback amplifiers and the output load capacitative ability is limited.
These parts will be particularly useful in portable applications where the chip select function can be used and the architectures are sure to be as various filters, as difference amplifiers, as load buffers, and as integrators. Apart from the freeing up of a pin for the low-power CS function, the internal connection also makes the layout simpler than when a dual op is being used in this way with a via from pin 1 having to run to pin 5 on the opposite corner of the IC. The parts are also priced without any kind of premium.
The MCP6275, MCP6285 and the MCP6295 are in production in PDIP-8, SOIC-8 and MSOP-8. The MSOP-8 pricing is $0.85 for the MCP6275, $0.65 for the MCP6285 and $0.71 for the MCP6295, all in 1000-piece lots.
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Sheet MCP6275
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Sheet MCP6285
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Sheet MCP6295