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TEA1202TS Fiches technique(PDF) 7 Page - NXP Semiconductors |
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TEA1202TS Fiches technique(HTML) 7 Page - NXP Semiconductors |
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7 / 24 page  2000 Jun 08 7 Philips Semiconductors Objective specification Battery power unit TEA1202TS When the output voltage becomes lower than the low limit of the window, a corrective action is taken by a ramp-up of the inductor current during a much longer time. As a result, the DC current level is increased and normal PWM control can continue. The output voltage (including ESR effect) is again within the predefined window. Figure 4 shows the spread of the output voltage window. The absolute value is mostly dependent on spread, while the actual window size (Vh − Vl) is not affected. For one specific device, the output voltage will not vary more than 2% (typical value). In low output power situations, the TEA1202TS will switch over to PFM (discontinuous conduction) operating mode. In this mode, regulation information from an earlier PWM operating mode is used. This results in optimum inductor peak current levels in the PFM mode, which are slightly larger than the inductor ripple current in the PWM mode. As a result, the transition between PFM and PWM mode is optimum under all circumstances. In the PFM mode the TEA1202TS regulates the output voltage to the high window limit as shown in Fig.3. Synchronous rectification For optimum efficiency over the whole load range, synchronous rectifiers inside the TEA1202TS ensure that during the whole second switching phase, all inductor current will flow through the low-ohmic power MOSFETs. Special circuitry is included which detects when the inductor current reaches zero. Following this detection, the digital controller switches off the power MOSFET and proceeds with regulation. Start-up Start-up from low input voltage in the boost mode is realized by an independent start-up oscillator, which starts switching the N-type power MOSFET as soon as the low-battery detector detects a sufficiently high voltage. The inductor current is limited internally to ensure soft-starting. The switch actions of the start-up oscillator will increase the output voltage. As soon as the output voltage is high enough for normal regulation, the digital control system takes control over the power MOSFETs. Undervoltage lockout As a result of too high a load or disconnection of the input power source, the output voltage can drop so low that normal regulation cannot be guaranteed. In this event, the device switches back to start-up mode. If the output voltage drops even further, switching is stopped completely. Shut-down When the shut-down input is set HIGH, the DC/DC converter disables both switches and power consumption is reduced to a few microamperes. Power switches The power switches in the IC are one N-type and one P-type power MOSFET, both having a typical drain-to-source resistance of 100 m Ω. The maximum average current in the power switches is 1.0 A at Tamb =80 °C. Temperature protection When the DC/DC converter operates in the PWM mode, and the die temperature gets too high (typical value is 160 °C), the converter and both LDOs stop operating. They resume operation when the die temperature falls below 90 °C again. As a result, low frequent cycling between the on and off state will occur. It should be noted that in the event of device temperatures at the cut-off limit, the application differs strongly from maximum specifications. Current limiters If the current in one of the power switches exceeds the programmed limit in the PWM mode, the current ramp is stopped immediately and the next switching phase is entered. Current limiting is required to keep power conversion efficient during temporary high loads. Furthermore, current limiting protects the IC against overload conditions, inductor saturation, etc. The current limiting level is set by an external resistor which must be connected between pin ILIM and ground for downconversion, or between pins ILIM and UPOUT/DNIN for upconversion. |
Numéro de pièce similaire - TEA1202TS |
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Description similaire - TEA1202TS |
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