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LNBH29QTR Datasheet(PDF) 5 Page - STMicroelectronics |
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LNBH29QTR Datasheet(HTML) 5 Page - STMicroelectronics |
5 / 31 page DocID023065 Rev 3 5/31 LNBH29 Application information 2 Application information This IC has a built-in DC-DC step-up converter that, from a single source from 9 V to 17.5 V, generates the voltages (VUP) that allow the linear post-regulator to work with a minimum dissipated power of 0.5 W typ. @ 500 mA load (the linear post-regulator drop voltage is internally kept at VUP - VOUT = 1 V typ.). The IC is also provided with an undervoltage lockout circuit that disables the whole circuit when the supplied VCC drops below a fixed threshold (4.7 V typically). The step-up converter is provided with a soft-start function which reduces the inrush current during startup. The SS time is internally fixed at 4 ms typ. to switch from 0 to 13 V and 6 ms typ. to switch from 0 to 18 V. 2.1 DiSEqC™ data encoding The LNBH29 series includes two versions with different DiSEqC control pin solutions: LNBH29 with DSQIN pin and LNBH29E with EXTM pin. The LNBH29 is provided with the DSQIN logic input pin (TTL compatible) to be controlled by an external DiSEqC data envelope source which activates the internal 22 kHz tone generator factory trimmed. This guarantees the tone output waveform in accordance with the DiSEqC standards. The LNBH29E is provided with the EXTM analogic modulation input pin to be connected to an external 22 kHz DiSEqC tone source. The tone output waveform depends on the characteristics of an external signal injected by means of the EXTM pin. 2.2 LNBH29: data encoding by external DiSEqC envelope control through the DSQIN pin If an external DiSEqC code envelope source is available, it is possible to use the internal 22 kHz generator activated during the tone transmission by connecting the DiSEqC envelope source to the DSQIN pin (see Section 5: Typical application circuits). In this way, the internal 22 kHz signal is superimposed to the VOUT DC voltage to generate the LNB output 22 kHz tone. During the period in which the DSQIN is kept HIGH, the internal control circuit activates the 22 kHz tone output. The 22 kHz tone on the VOUT pin is activated with about 6 µs delay from the DSQIN TTL signal rising edge, and it stops with a delay time in the range of 15 µs to 60 µs after the 22 kHz TTL signal on DSQIN has expired (refer to Figure 2). Figure 2. Tone enable and disable timing (using envelope signal) AM10427v1 ~ 6 µs 15 µs ~ 60 µs DSQIN Tone Output |
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