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T H AT Corporation
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· · · · · OutSmartsÔ technology tames clipping behavior into single-ended loads Pin-compatible with SSM2142 Balanced, floating output delivers transformer-like behavior Stable when driving long cables and capacitive loads THAT 1430 delivers low output offset voltage using single capacitor · · · · · · · · ·
OutSmartsä Balanced Line Drivers
THAT 1420, 1430 APPLICATIONS
Differential Line Driver Audio Mix Consoles Distribution Amplifiers Audio Equalizers Dynamic Range Processors Digital Effects Processors Telecommunications Systems Instrumentation Hi-Fi Equipment
Description
The THAT 1420 and 1430 are a new generation of audio differential line drivers with improved performance over conventional cross-coupled monolithic designs. Both models exhibit low noise and distortion, high slew rate, stability under difficult loads, wide output swing, and have outputs which are short-circuit protected. In addition both models incorporate patented OutSmartsÔ technology, a dual feedback-loop design that prevents the excessive ground currents typical of cross-coupled output stages (CCOS) when clipping into single-ended loads1. To overcome this problem, the THAT 1420 and 1430 use two individual negative-feedback loops to separately control the differential output voltage and common mode output currents, making the design inherently more stable and less sensitive to component tolerances than the CCOS. Most importantly, the dual-feedback design prevents the loss of common-mode feedback that plagues the CCOS designs, avoiding the excessive ground currents and overly-distorted output waveform that can result when driving single-ended loads. Where minimum output offset voltage with minimum parts count is desired, the THAT 1430 further improves over existing designs. In conventional CCOS circuits, two relatively high-value electrolytic capacitors are required to reduce the offset voltage. By contrast, the THAT 1430 topology requires only a resistor and a single film or ceramic capacitor to achieve the same effect at lower parts count and price.
DIP Pin Number
OutCEXT Sens+ 5k In+ Din+ Cin+ CinGnd 5k Din10k Dout10k 10p 20k
THAT 1420
10k 50
SO Pin Number
3 4 5 6 11 12 13 14
1420 Pin Name
OutSensGnd In Vee Vcc Sens+ Out+
1430 Pin Name
OutCap2 Gnd In Vee Vcc Cap1 Out+
Vcc
1 2 3 4 5
CEXT
AD & AC
Dout+ 10k 10k 10k 20k Sens-
Vee
50 Out+
6 7 8
Figure 1. THAT 1420 Equivalent Circuit Diagram
Table 1. THAT 1420/1430 pin assignments
1. See Gary Hebert’s paper, An Improved Balanced, Floating Output Driver IC, presented at the 108th AES Convention, Feb. 2000
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 2
THAT1420/1430 Balanced Line Driver Preliminary Information
SPECIFICATIONS 2 Absolute Maximum Ratings (T A = 25°C)
Positive Supply Voltage (Vcc) Negative Supply Voltage (Vee) Output Short Circuit Duration Power Dis.