L4938E Datasheet L4938E | P4-P6

Obsolete Product(s) - Obsolete Product(s)

ELECTRICAL CHARACTERISTICS

(Continued)

Symbol Parameter Test Condition Min. Typ. Max. Unit

ENABLE INPUT

ENL

Enable Input Low Voltage

(Output 2 Active)

-20 1 V

ENH

Enable Input High Voltage 1.4 20 V

ENhyst

Enable Hysteresis 20 30 60 mV

EN LOW

Enable Input Current Low V

= 0 -20 -8 -3 µA

EN HIGH

Enable Input Current High V

= 1.1 to 7V; T

< 130°C; -1 0 1 µA

= 1.1 to 7V;

= 130 to 150°C;

-10 0 10 µA

RESET CIRCUIT

Reset Theresold Voltage

(note4)

= ∞ 4.5 V

-0.3 V

-0.2 V

= 0 3.65 3.8 3.95 V

RTH

Reset Theresold Hysteresis R

= ∞ 30 60 120 mV

RD min

Reset Pulse Delay C

RES

= 47nF; t

≤ 30µs; (note 5) 40 60 100 ms

RD nom

Reset Pulse Delay C

RES

= 47nF; (note 6) 60 100 140 ms

Reset Reaction Time C

RES

= 47nF 10 50 150 µs

Pull Down Capability of the

Discharge circuit

OUT1

< V

3615mA

Charge Current V

OUT1

> V

-1.3 -1 0.7 µA

RESL

Reset Output Low Voltage R

RES

= 10KΩ to V

OUT1

≥ 1.5V

0.4 V

RESH

Reset Output High Leakage

current

RES

= 5V 1 µA

SENSE COMPARATOR

Functional Range -20 20 V

SIT

Sense Threshold Voltage Falling Edge; T

<130°C 1.08 1.16 1.24 V

Falling Edge; T

<130 to 150°C 1.05 1.16 1.29 V

SITH

Sense Threshold Hysteresis 10 30 60 mV

SOL

Sense Output Low Voltage V

≤ 1.05V; R

=10KΩ

connected to 5V; V

≥ 5V

0.4 V

SOH

Sense Output Leakage V

= 5V; V

≥ 1.5V 1 µA

SI HIGH

Sense Input Current High V

= 1.1 to 7V; T

<130°C-101µA

= 1.1 to 7V; T

<130 to 150°C-10 0 10 µA

SI LOW

Sense Input Current Low V

= 0V -20 -8 -3 µA

Note :

4) The reset threshold can be programmed continuously from typ 3.8V to 4.7V by changing a value of an external resistor from pin PR to GN

5) This is a minimum reset time according to the hysteresis of the comparator. Delay time starts with V

OUT1

exceeding V

6) This is the nominal reset time depending on the discharging limit of C

(saturation voltage) and theupper threshold of the timer comparator.

Delay time starts with V

OUT1

exceeding V

7) The leakage of C

must be less than 0.5mA (2V). If an external resistor between C

and V

OUT1

is applied, the leakage current may be

increased. The external resistor should have more than 30K

Ω

for stability: Cs

≥

F, C01

≥

F, C02

≥

F, ESR

≤

Ω

(designed target) For details see application note.

8) For transients exceeding 20V or -20V external protection is required at the Pins SI and EN as shown at Pin EN. The protection proposed will

provide proper function for transients in the range of

200V. If the zener diode is omitted the external resistor should be raised to 200K

Ω

to limit the current to 1mA. Without the zener diode, the function 20V or -20V can not be guaranteed.

L4938E - L4938ED - L4938EPD

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Obsolete Product(s) - Obsolete Product(s)

FUNCTIONAL DESCRIPTION

The L4938E/ED/EPD is a monolithic integrated

dual voltage regulator, based on the STM modu-

lator voltage regulator approach. Several out-

standing features and auxiliary functions are im-

plemented to meet the requirements of supplying

microprocessor systems in automotive applica-

tions. Nevertheless, it is suitable also in other ap-

plications where two stabilized voltages are re-

quired. The modular approach of this device

allows to get easly also other features and func-

tions when required.

Standby Regulator

The standby regulator uses an Isolated collector

Vertical PNP transistor as a regulating element.

With this structure very low dropout volotage at

currents up to 100mA is obtained. The dropout

operation of the standby regulator is maintained

down to 3V input supply voltage. The output volt-

age is regulated up to the transient input supply

voltage of 40V. With this feature no functional in-

terruption due to overvoltage pulses is generated.

In the standby mode when the output 2 is dis-

abled, the current consumption of the device (qui-

escent current) is less than 90

A (14V supply

voltage).

To reduce the quiescent current peak in the un-

dervoltage region and to improve the transient re-

sponse in this region, the dropout voltage is con-

trolled. A second regulation path will keep the

output voltage without load below 5.5V 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 400mA. The output voltage

is internally fixed to 5V if ADJ is connected to

OUT2

The output 2 regulator can be switches OFF via

the enable input.

REG1

1.23V REFERENCE

REG2

1.23V

RESET

1.4V

1.23V

SENSE

VS1

VS2

RES

ADJ

OUT2

OUT1

GND

D94AT079A

15V

100K

(Note 8)

for example

BZX97C15

CT (Note 7)

OUT1

Figure 1. Application Diagram.

1.23V

D94AT080

OUT2

ADJ

total 100K

typical

Figure 2.

L4938E - L4938ED - L4938EPD

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Obsolete Product(s) - Obsolete Product(s)

Connecting a resistor divider R

, R

to the ADJ,

OUT2 pin the output voltage 2 can be pro-

grammed to the value of

OUT2

OUT1







(

ADJ

)

⋅

ADJ







with R

ADJ

= 60K to 150K and V

OUT1

= 4.95 to

5.05V.

For an exact calculation the temperature coeffi-

cient (Tc -2000pprm) of the internal resistor

ADJ

) must be taken into account. Pin ADJ in this

mode should not have a capacitive burden be-

cause this would reduce the phase margin of the

regulator loop.

Reset circuit

The reset circuit supervises the standby output

voltage. The reset output (RES) is defined from

OUT

≥

1V.

Even if V

is lacking, the reset generator is sup-

plied by the output voltage V

OUT1

The reset threshold of 4.7V is defined with the in-

ternal reference voltage (note 9) and standby out-

put divider, when pin PR is left open. The reset

threshold voltage can be programmed in the

range from 3.8V to 4.7V by connecting an exter-

nal resistor from pin PR to GND.

The value of the programming resistor R

can

be calculated with:

22K

4.7K

−

92.9K,

3.8V

≤

4.7V

The reset pulse delay time t

, is defined with the

charge time of an external capacitor C

RDmin

⋅

0.6V

(note 5)

RDnom

⋅

1.4V

(note 6)

The reaction time of the reset circuit originates

from the noise immunity. Standby output voltage

drops below the reset threshold only a bit longer

than the reaction time results in a shorter reset

delay time. The nominal reset delay time will be

generated for standby output voltage drops longer

than approximately 50

The minimum rset time is generated if reset con-

dition only occures for a short time triggering a re-

set pulse but not completely discharging C

. The

reset can be related to output2 on request. If

higher charge currents for the reset capacitor are

required a resistors from Pin C

to OUT1, may be

used to increase the current. We recommended

the use of 10K

Ω

to 5V as an output pull up.

Sense Comparator

The sense comparator compares an input signal

with an internal voltage reference of typical 1.23V.

The use of an external voltage divider makes this

comparator very flexible in the application. It can

be used to supervise the input voltage either be-

fore or after the protection diode and to give addi-

tional information to the microprocessor like low

voltage warnings. We recommended the use of

10K

Ω

to 5V as an output pull up.

Note 9:

The reference is alternatively supplied from V

or V

OUT1

. If one supply

is present, the reference is operating.

Thermal Protection

Both outputs are provided with an overtempera-

ture shut down regulation power dissipation down

to uncritical values.

Output 2 will shut down approximately 10K before

output 1.

Under normal conditions shut down of output 2

will allow the chip to cool down again. Thus out-

put 1 will be unaffected.

The thermal shut down reduces the output volt-

ages until power dissipation and the flow of ther-

mal energy out of the chip balance.

Transient Sensitivity

In proper operation (V

OUT

> 4.5V) the reference is

supplied by V

OUT1

thus reducing sensitivity to in-

put transients.

Precise Data will be issued as soon as samples

are available.

L4938E - L4938ED - L4938EPD

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L4938E

Mfr. #:

Buy L4938E

Manufacturer:

STMicroelectronics

Description:

LDO Voltage Regulators Dual 5V Very LDO

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L4938E