2.70 VOLT ULTRA LOW DROPOUT
REGULATOR
Issue 2 June 1997
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 2.70 to 12 volts, this
device provides an output voltage of 2.70 volts.
The ZLDO270 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.
Low Battery Flag
ZLDO270
FEATURES
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Very low dropout voltage
6mV dropout at 10mA output
30mV dropout at 100mA output
100mV dropout at 300mA output
2.70 volt fixed output
Other voltages available
Low quiescent current
1mA quiescent (typ) at 300mA output
Low battery flag
Shutdown control
Surface mount package
APPLICATIONS
Battery powered devices
Portable instruments
Portable communications
Laptop/Palmtop computers
Electronic organisers
Vin
LOW BATTERY
COMPARATOR
THERMAL
SHUTDOWN
Vo
Shutdown
Control
SHUTDOWN
BIAS
CIRCUIT
OUTPUT
DRIVE
Cs
BANDGAP
REFERENCE
Shaping
Gnd
ZLDO270
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:-
V
O
change x
1000000
V
O
x 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 V
out
measured
at the nominal input V
in
= V
out
+ 1V
4.
Guaranteed by design.
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.
Embedded System
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