UZLDO500T8TA - Zetex Semiconductors

DEVICE DESCRIPTION

The ZLDO Series low dropout linear

regulators operate with an exceptionally

low dropout voltage, typically only 30mV

with a load current of 100mA. The regulator

series features output voltages in the range

2.7 to 18 volts, this device provides an output

voltage of 5.0 volts.

The ZLDO500 consumes a typical quiescent

current of only 1mA at its maximum rated

output current of 300mA. A battery low flag

is available to indicate potential power fail

situations. If the input voltage falls to within

200mV of the regulated output voltage then

the error output pulls low. The device also

features an active high disable control. Once

disabled the ZLDO quiescent current falls to

typically 11µA.

The ZLDO devices are packaged in Zetex

SM8 8 pin small outline surface mount

package, ideal for applications where space

saving is important. The device low dropout

voltage, low quiescent current and small size

make it ideal for low power and battery

powered applications. Battery powered

circuits can make particular use of the low

battery flag and shutdown features.

FEATURES

•Very low dropout voltage

•6mV dropout at 10mA output

•30mV dropout at 100mA output

•100mV dropout at 300mA output

• 5.0 volt fixed output

•Other voltages available

• Low quiescent current

•1mA quiescent at 300mA output

• Low battery flag

• Shutdown control

• Surface mount package

APPLICATIONS

• Battery powered devices

• Portable instruments

• Portable communications

• Laptop/Palmtop computers

• Electronic organisers

5.0 VOLT ULTRA LOW DROPOUT

REGULATOR

ISSUE 2 - JULY 1997

LOW BATTERY

COMPARATOR

Low Battery Flag

Vin

OUTPUT

DRIVE

BIAS

CIRCUIT

SHUTDOWN

THERMAL

SHUTDOWN

Shutdown

Control

BANDGAP

REFERENCE

Shaping

Gnd

ZLDO500

4-80

ZLDO500

ABSOLUTE MAXIMUM RATING

Input Supply

Voltage Range -0.3 to 20V

Shutdown Input

Voltage Range -0.3 to Vin

Low Battery Output

Voltage Range -0.3 to 20V

Output Current 300mA

Operating Temperature -40 to 85°C

Storage Temperature -55 to 150°C

Power Dissipation

(Tamb=25°C) 2W (Note 1)

Parameter SYMBOL CONDITIONS MIN TYP MAX UNITS

Output voltage VoVin=6.0V 4.9 5.0 5.1 V

Output voltage

temperature coefficient Vo

∆TVin=6.0V

(Note 2, Note 4)

100 250 ppm/°C

Line regulation ∆VoVin=6.0 to 20V 20 70 mV

Load regulation ∆VoIL=10 to 300mA

Vin=6V

70 123 mV

Dropout voltage

(Note3)

Vin-VoIL=10mA

IL=100mA

IL=300mA

100

200

Quiescent current IqVin=6.0V, IL=0 0.63 1 mA

Quiescent current

at shutdown

Iqs Vin=6.0V, IL=0,

Vshdn=Vin

11 30 µA

Shutdown control input

current

Iins Vshdn=Vin=6.0V 2 10 µA

Shutdown control

threshold voltage

Vts Vin=6.0V

low(on)

high(off) 1.5

0.4 V

Output current in

shutdown mode

(Note4)

ILs Vin=20V

Vo=Gnd

50 100 nA

Output noise voltage

(Note4)

enVin=6.0V

f=10Hz

to100kHz,

IL=100mA

190 µV RMS

Low battery detect

voltage

Vin(bld) VO +

0.2V

VO +

0.4V

Low battery flag

output voltage

Vbl Ibl=100µA,

Vin<Vo+200mV

0.16 0.4 V

Low battery flag

leakage current

Ibl Vbl=6V,

Vin>Vo+400mV

0.1 1 µA

ELECTRICAL CHARACTERISTICS

TEST CONDITIONS (Unless otherwise stated) Tamb

=25°C,IL=10mA,Cs=10pF,Cout =1µF

4-81

ZLDO500

FUNCTIONAL DESCRIPTION

The ZLDO is a high performance, ultra low

dropout, low quiescent regulator. Available in

SM8 surface mount packaging, the device is

able to dissipate 2W(note 1) allowing

complete design flexibility with an input span

upto 20V and 300mA output current. The

device quiescent is 1mA (typ) at 300mA load

current. A low battery comparator signifies

impending battery failure, whilst a shutdown

function reduces quiescent current to a mere

11µA (typ). A precision bandgap reference

gives ± 2.5% output tolerance and good

temperature characteristics over the range

-40 to +85°C. AC performance is enhanced via

the use of a small external capacitor.

PIN DEFINITIONS

Pin 1 LBF - Low Battery Flag. An open

collector NPN output which pulls low on failing

input supply.

Pin 2 SC - Shutdown Control. This high

impedance logic compatible input disables the

regulator when taken high. It includes a diode

wired to Vin and so will pass current if taken

more than 0.5V above Vin.

Pin 3 Vin - Voltage Input. The power supply to

the regulator. The permissible input voltage

range is -0.3 to 20V. An input capacitor is not

mandatory but will be useful in reducing the

coupling of noise from input to output and

minimising the effect of sudden changes in load

current on the input voltage.

Pin 4 N/C - Not Connected. Not internally

connected and so can be left open or wired to

any pin without affecting the performance of the

regulator.

Pin 5 Vout - Voltage Output. The output of the

regulator. An output capacitor of 1uF or greater

and having low ESR should be wired in close

proximity to the regulator to ensure stability for

all loads.

Pin 6 D/C - Do Not Connect. This pin is wired

to an internal circuit node of the regulator. No

external connection should be made to this pin.

Pin 7 Gnd - Ground. The ground connection

of the regulator against which the output

voltage is referenced.

Pin 8 Spg - Shaping. The shaping node for

the error amplifier of the regulator. A

capacitor of 10pF wired from this pin to the

output pin (pin 5) gives optimum stability.

Improved AC can be achieved by reducing

the value of this capacitor but stability may

be impaired for some load conditions.

NOTES.

1. Maximum power dissipation of the device is calculated assuming the package is mounted on a

PCB measuring 2 inches square.

2 Output voltage temperature coefficient is calculated as:-

change

1000000

temperature

change

3. Dropout voltage is defined as the input to output voltage differential at which the circuit ceases

to regulate. The value is measured when the output voltage has dropped by 100mV from Vout

measured at the nominal input Vin = Vout + 1V

4. Guaranteed by design.

4-82

ZLDO500

Frequency (Hz)

Output Impedance vs. Frequency

Output Impedance (mΩ)

100 1K 10K 100K

200

800

400

1000

600

1200

C(out)=1µF

10pF

4.7pF

2.2pF

Shutdown Current (µA)

Shutdown Current vs. Temperature

Temperature ( °C)

-40 -20 0 100

Output Voltage (V)

Temperature ( °C)

Output Voltage Temperature Coefficient

-40 0 40 80

4.98

5.00

5.02

5.04

Frequency (Hz)

Ripple Rejection vs. Frequency

Ripple Rejection (dB)

100 1K 10K 100K

-20 20 60

Io=10mA

C(out)=1µF

10pF

4.7pF

2.2pF

100

4.99

4.97

5.01

5.03

Quiescent Current (µA)

Temperature ( °C)

Quiescent Current vs. Temperature

L.B.F. Operation Voltage (V)

Temperature ( °C)

Low Battery Flag Operating Point

700

680

660

640

620

600

580

540

-40 -20 0 100

5.27

5.25

5.24

5.23

5.22

5.28

5.26

-40 -20 0 100

720

560

20 40 60 80

20 40 60 80 20 40 60 80

V(in)=7V

1400

1600

1800

2000

V(in)=7V

Io=10mA

V(in)=7V

TYPICAL CHARACTERISTICS

4-83

ZLDO500

Dropout Voltage (mV)

180

160

140

120

100

0.1 1.0 10 100

Load Current (mA)

Dropout Voltage vs. Load Current

V(in)= 7V

200

220

1000

85 ° C

25 ° C

-40 °C

V(in)= 12V

V(in)= 7V

Io= 100mA

Time (µs)

Line Transient Response

0 200 400 600 800 1000

-1

Output Voltage Deviation (V)

0.5

-0.5

Io= 0mA

Io= 100mA

V(in)= 7V

0 200 400 600 800 1000

Time (µs)

Load Transient Response

Output Voltage Deviation

Safe Operating Area

SINGLE PULSE TEST Tamb =25

°C

1.0

0.1

0.01

Load Current (A)

Input-Output Differential Voltage (V)

2 5 10 201

DC 1s 0.1s 10ms

TYPICAL CHARACTERISTICS

Operation in shaded area is not guaranteed

4-84

1). Operation From A Low Voltage

Battery Pack

Fig.1 shows the ZLDO500 regulator being

used to stabilise the output of a 6V battery

pack. The ultra low dropout voltage of only

100mV at full load (300mA) given by the

regulator allows the minimum number of

cells to be used in the pack and also

maximises the energy that can be removed

from the battery before the output of the

regulator starts to fail.

At a load current of 100mA the dropout

voltage falls to around 30mV. The endurance

of the battery pack is not only dependent on

dropout voltage. When operating, some low

dropout regulators can consume high

quiescent currents, sometimes approaching

as much as a tenth of their maximum load

current specification when approaching

dropout conditions. Despite its 300mA output

rating, when enabled the ZLDO500 consumes

typically only 630uA regulating normally and

3mA when the input falls too low for

regulation.

2). Post Converter Regulation

A common problem with multiple output

switch mode converters is that only one

output can be used in the feedback control

loop of the switching regulator. Thus only

one output is fully regulated. All other

outputs are prone to tracking errors that

occur if the load on any output change

significantly. By ensuring close coupling of all

transformer windings and minimising the

impedance of all outputs, these errors can be

reduced but never eliminated. A simple way

round this problem is to wind the switching

regulator transformer to give a slightly higher

voltage than required and regulate down

from this to the desired voltage with a linear

regulator. This is indicated in Figure 2. To

keep losses low and so maintain the

advantages of a switch mode supply, it is

important that the voltage drop across this

regulator is kept as low as possible, i.e. just

high enough to compensate for the poor

output impedance of the switching power

supply but no higher. The low dropout

Spg

D/C

Vout

LBF

Vin

N/C

Gnd

ZLDO500

6V C2

1uF

10pF

100nF Output

+5V

Spg

D/C

Vout

LBF

Vin

N/C

Gnd

ZLDO500

1uF

10pF

+12V Out

0V Out

220uF

+5.0V Out

TR1

Feedback

Switching

Regulator

Voltage

Figure 2

ZLDO500

APPLICATIONS

Figure 1

4-85

voltage of the ZLDO500 allows this circuit

technique to be implemented very effectively,

giving a highly stable and accurate low noise

supply.

3). Logic Controlled Power Supply

Figure 3 shows all that is necessary to allow

a microprocessor to control a power supply

based on the ZLDO500 The Shutdown Control

pin (pin 2), is a logic compatible input that

disables the regulator when a voltage in

excess of 1.5V is applied. The current required

to drive this input is less than 10µA. When the

regulator is shutdown in this way, the

quiescent current of the ZLDO500 falls to

around 11µA. This makes the regulator

suitable for a wide range of battery powered

applications where intermittent operation

occurs. The shutdown control pin should not

be taken to a voltage higher than Vin if low

quiescent supply current is important. The

shutdown control is a high impedance input

and so if not required, should be wired to the

ground pin (pin 7).

4). Over Temperature Shutdown

The ZLDO500 regulator includes an over

temperature shutdown circuit that disables

the regulator if its chip temperature should

exceed 125°C for any reason. Although

intended to provide a limited guard against

excessive internal power dissipation, this

circuit will shut down the regulator if its

ambient rises above 125°C. Thus, the

regulator could be used to disable a circuit in

the event of the ambient temperature within

which the circuit is mounted becoming too

high. Any internal power dissipation caused

as a result of supplying load current, will

reduce the ambient temperature at which

shutdown occurs. Note that to achieve the

extremely low dropout voltage and high

current performance provided by the

ZLDO500

APPLICATIONS

Spg

D/C

Vout

LBF

Vin

N/C

Gnd

IC2

ZLDO500

1uF

10pF

100nF

+5V

Microproc.

System

Supply Input

Vin Vout

Gnd

IC1

ZSR500

+6.7V

to 20V

Figure 3

4-86

Figure 4

ZLDO500 devices, the parts can be damaged

by sustained output shorts or excessive loads

when combined with high input supply

voltages. To ensure reliable operation, keep

loads within the SOA graph boundaries

Indicated in the typical characteristics.

5). Low Battery Flag

The ZLDO500 provides an output called Low

Battery Flag (LBF). Unlike many regulators

that only signal that they are falling out of

regulation, the LBF output of the ZLDO500

series indicates that the voltage drop across

the regulator has fallen to less than typically

300mV and so supply failure is imminent.

This improved warning gives both more time

for the system supplied to shutdown

gracefully and maintains regulation while

this happens. This could be a vital point if

measurements are under way and must be

Spg

D/C

Vout

LBF

Vin

N/C

Gnd

ZLDO500

6V C2

1uF

10pF

100nF

100k

+5V

Microproc.

System Interrupt

Input

ZLDO500

APPLICATIONS

4-87

SM8 Package Suffix – T8

Top View –

Pin 6 must be left floating

SEE PIN DEFINITIONS

CONNECTION DIAGRAM

ORDERING INFORMATION

Part Number Package Part Mark

ZLDO500T8 SM8 ZLDO500

ZLDO500

4-88