L4938ED L4938EPD Advanced voltage regulator Features ■ Enable and sense inputs (EN, SI) protected against negative transients down to -5 V Reset threshold adjustable from 3.8 V to 4.7 V Extremely low quiescent current, 65 µA (less than 90 µA) in standby mode Operating DC supply voltage range 5 V - 28 V Operating transient supply voltage up to 40 V High precision standby output voltage 5 V ± 1% with 100 mA current capability Output 2 voltage 5 V ± 2% with 400 mA current capability (ADJ wired to VOUT2) Output 2 voltage adjustable by external voltage divider Output 2 disable function for standby mode Description The L4938ED and L4938EPD are monolithic integrated dual voltage regulators with two very low dropout outputs and additional functions such as power-on reset and input voltage sense. They are designed for supplying microcomputer controlled systems especially in automotive applications. Device summary Order codes

Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Standby regulator Thermal protection Package and packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1 4.2

List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pin definitions and functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....

List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Configuration diagram (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 OUT2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....

Block diagram and pin description Block diagram and pin description Figure 1. Block diagram Configuration diagram (top view)

Block diagram and pin description Table 2. Pin definitions and functions PIn number Name Supply voltage (400 mA regulator) Supply voltage (100 mA regulator, reset, sense) Sense input Reset threshold programming Reset delay capacitor Enable (low activates the 400 mA regulator) Reset output Sense output 100 mA regulator output Feedback of 400 mA regulator 400 mA regulator output Not connected

Electrical specifications Electrical specifications Absolute maximum ratings Stressing the device above the ratings listed in the “Absolute maximum ratings” tables may cause permanent damage to the device. These are stress ratings only and operation of the device at these or any other conditions above those indicated in the Operating sections of this specification is not implied. Exposure to the conditions in this section for extended periods may affect device reliability. Refer also to the STMicroelectronics SURE Program and other relevant quality documents. Table 3. Absolute maximum ratings...

Electrical specifications Thermal data Table 4. Thermal data Thermal resistance junction to ambient Thermal resistance junction to case Typical value soldered on a PC board with 8 cm2 copper ground plane (35 mm thick). Electrical characteristics VS = 14 V; Tj = -40 to 150 °C, unless otherwise specified. Table 5. Test condition Supply output voltage Drop output voltage 1 IOUT1 = 1 to 100 mA (after regulation setting) Quiescent current in standby mode Test condition Enable = low; VS = 6 to 28 V; IO2 = 5 to 400 mA Output voltage 2 ADJ connected to OUT2 Drop output voltage 2 Adjust input resistance...

Electrical specifications OUT1, OUT2 Parameter Test condition VS = 6 to 28 V; IO1 = 1 mA, IO2 = 5 mA, (after regulation setting) Line regulation Enable input Parameter Test condition Enable input low voltage (output 2 active) Enable input high voltage Enable hysteresis Enable input current low Enable input current high Reset circuit Parameter Test condition Reset threshold hysteresis Reset pulse delay Reset pulse delay Reset reaction time Pull down capability of the discharge circuit Charge current Reset output low voltage Reset output high leakage current 1. The reset threshold can be programmed...

Electrical specifications Table 10. Symbol VSI Sense comparator Parameter Test condition Functional range Sense threshold voltage Sense threshold hysteresis Sense output low voltage Sense output leakage Sense input current high Sense input current low

Application information Application information Application diagram 1. The leakage of CT must be less than 0.5 mA (2 V). If an external resistor between CT and V OUT1 is applied, the leakage current may be increased. The external resistor should have more than 30 KΩ. For stability: Cs ≥ 1 µF, C01 ≥ 10 µF, C02 ≥ 10 µF, ESR ≤ 5Ω (designed target). 2. For transients exceeding 20 V or -20 V external protection is required at the pins SI and EN as shown at pin EN. The protection proposed provides proper function for transients in the range of ±200 V. If the zener diode is omitted the external resistor...

Application information In the standby mode when the output 2 is disabled, the current consumption of the device (quiescent current) is less than 90 µA (14 V supply voltage). To reduce the quiescent current peak in the undervoltage region and to improve the transient response in this region, the dropout voltage is controlled. A second regulation path keeps the output voltage without load below 5.5 V even at high temperatures. Output 2 voltage The output 2 regulator uses the same output structure as the standby regulator but rated for the output current of 400 mA. The output voltage is internally...