Page 1
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 3.3 volts.
The ZLDO330 consumes a typical quiescent
current of only 560µA and is rated to supply
load currents up to 300mA. A battery low flag
is available to indicate potential power fail
situations. If the input voltage falls to within
300mV 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
•
3.3 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
3.3 VOLT ULTRA LOW DROPOUT
REGULATOR
ISSUE 2 - MAY 1997
ZLDO330
LOW BATTERY
COMPARATOR
Low Battery Flag
Vin
OUTPUT
DRIVE
BIAS
CIRCUIT
SHUTDOWN
THERMAL
SHUTDOWN
Shutdown
Control
BANDGAP
REFERENCE
Vo
Shaping
Gnd
Cs
4-62
Page 2
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)
ZLDO330
ELECTRICAL CHARACTERISTICS
TEST CONDITIONS (Unless otherwise stated) T
amb
=25°C,IL=10mA,Cs=10pF,C
out
=1µF
Parameter SYMBOL CONDITIONS MIN. TYP. MAX. UNITS
Output voltage V
o
Vin=4.3V 3.2 3.3 3.4 V
Output voltage
temperature coefficient
V
o
∆T
Vin=4.3V
(Note 2, Note 4)
100 250 ppm/°C
Line regulation
∆
V
o
Vin=4.3 to 20V 15 52 mV
Load regulation
∆
V
o
IL=10 to 300mA
V
in
=4.3V
45 78 mV
Dropout voltage
(Note3)
V
in-Vo
IL=10mA
I
L
=100mA
I
L
=300mA
6
30
100
10
75
200
mV
Quiescent current I
q
Vin=4.3V, IL=0 0.56 1 mA
Quiescent current
at shutdown
I
qs
Vin=4.3V, IL=0,
V
shdn=Vin
11 30
µA
Shutdown control
input
current
I
ins
V
shdn=Vin
=4.3V 2 10
µA
Shutdown control
threshold voltage
V
ts
Vin=4.3V
low(on)
high(off) 1.5
0.4 V
Output current in
shutdown mode
(Note4)
I
Ls
Vin=20V
V
o
=Gnd
50 100 nA
Output noise voltage
(Note4)
e
n
Vin=4.3V
f=10Hz to100kHz,
I
L
=100mA
190
µV RMS
Low battery detect
threshold
V
in(bld)
V
out
+
0.2V
V
out
+
0.4V
V
Low battery flag
output voltage
V
bl
Ibl=100µA,
V
in<Vo
+200mV
0.16 0.4 V
Low battery flag
leakage current
I
bl
Vbl=6V,
V
in>Vo
+400mV
0.1 1
µA
4-63
Page 3
ZLDO330
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.
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.
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.
4-64
Page 4
ZLDO330
Temperature ( °C)
Quiescent Current vs. Temperature
Temperature ( °C)
Shutdown Current vs. Temperature
Temperature ( °C)
Output Voltage (V)
Output Voltage Temperature Coefficient
Io=10mA
Quiescent Current (
µ
A)
V(in)=5V
V(in)=5V
Shutdown Current (
µ
A)
Output Impedance (m
Ω
)
Frequency (Hz)
Output Impedance vs. Frequency
Ripple Rejection (dB)
Frequency (Hz)
Ripple Rejection vs. Frequency
L.B.F. Operation Voltage (V)
Temperature ( °C)
Low Battery Flag Operating Point
35
40
45
50
55
30
25
20
15
10
5
0
100
1K 10K 100K
400
440
480
520
560
600
640
680
-40
0-20 20 40 60 80
3.28
3.30
3.27
3.32
3.29
-40
-20 0 20 6040 80
10
12
16
14
8
-20
-40
08020 40 60
6
3.56
3.57
3.58
3.61
3.60
3.59
-40
-20 0 20 6040 80
0
200
400
600
800
1000
1200
1400
100K
100
10K1K
C
(out)
=1µF
10pF
4.7pF
2.2pF
C(out)=1µF
10pF
4.7pF
2.2pF
100
V(in)=7V
Io=10mA
3.55
100
V(in)=5V
3.31
3.33
100
TYPICAL CHARACTERISTICS
4-65
Page 5
ZLDO330
Time (µs)
Line Transient Response
Time (µs)
Output Voltage Deviation (V)
Load Transient Response
0
0200
400 600
1000
800
0
-0.4
-0.2
0.2
120
040
80
200
160
Output Voltage Deviation (V)
Dropout Voltage (mV)
Load Current (mA)
Dropout Voltage vs. Load Current
40
60
80
100
120
20
0
0.1 1.0
10 100
1000
0.4
-0.4
0.8
85 °C
25 °C
-40 °C
V
(in)
=10V
V
(in)
=5V
Io=100mA
1.0
0.1
0.01
SINGLE PULSE TEST T
amb
= 25 °C
Load Current (AMPS)
Input-Output Differential Voltage (VOLTS)
Safe Operating Area
2 5 10 201
Operation in shaded area is not guaranteed
Output Voltage Deviation
V
(in)
=5V
IO=100mA
IO=0mA
Output Voltage Deviation
DC
1s
0.1s
10ms
TYPICAL CHARA CTERIST ICS
4-66
Page 6
ZLDO330
1). Simple 3.3V Supply
Using a circuit such as Figure 1, the ZLDO330
can easily provide a 3.3V logic supply from an
available 5V rail where most standard
regulators could not guarantee correct
operation. Although this approach is not
particularly energy efficient, if the load taken
at 3.3V is not too large, then the added
complexity and cost of a 3.3V switching
converter may not be justifiable and so this
linear solution can be preferable. This circuit
will also give far less noise than a switching
regulator which can be important when
handling low level analogue signals or low
voltage measurements.
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 changes 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
voltage of the ZLDO330 allows this circuit
technique to be implemented very effectively,
giving a highly stable and accurate low noise
supply.
APPLICATIONS
Spg
D/C
Vout
LBF
SC
Vin
N/C
Gnd
IC1
ZLDO330
C2
1uF
C1
10pF
C3
100nF
+5V In +5V Out
+3.3V Out
0V Out0V In
Figure 1
Spg
D/C
Vout
LBF
SC
Vin
N/C
Gnd
ZLDO330
C2
1uF
C1
10pF
+ 5V Out
0V Out
C4
220uF
C5
220uF
+ 3.3 V Out
TR1
Feedback
Switching
Regulator
Voltage
D1
D2
Figure 2
4-67
Page 7
ZLDO330
3). Low Battery Flag
The ZLDO330 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 ZLDO330
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 completed accurately
for instance. The LBF output is driven by an
open collector NPN transistor which pulls low
when the supply to the regulator is failing.
Figure 3 shows this output being used. Note
that resistor R1 is necessary only if the
interrupt logic does not include a pull-up
resistor.
4). Over Temperature Shutdown
The ZLDO330 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 ZLDO
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.
APPLICATIONS
Spg
D/C
Vout
LBF
SC
Vin
N/C
Gnd
ZLDO330
4.8V
C2
1uF
C1
10pF
C3
100nF
R1
100k
0V
+3.3V
Microproc.
System
Interrupt
Input
Figure 3
4-68
Page 8
ZLDO330
5). Logic Controlled Power Supply
Fig.4 shows all that is necessary to allow a
microprocessor to control a power supply
based on the ZLDO330. 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 10uA. When the
regulator is shutdown in this way, the
quiescent current of the ZLDO330 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).
APPLICATIONS
Spg
D/C
Vout
LBF
SC
Vin
N/C
Gnd
IC2
ZLDO330
C2
1uF
C1
10pF
C3
100nF
0V
+3.3V
Microproc.
System
Switched
Supply Input
Vin Vout
Gnd
IC1
ZSR330
Output
0V
+5V
to 20V
Figure 4
4-69
Page 9
SM8 Package Suffix – T8
Top View –
Pin 6 must be left floating
SEE PIN DEFINITIONS
CONNECTION DIAGRAM
ORDERING INFORMATION
Part Number Package Part Mark
ZLDO330T8 SM8 ZLDO330
ZLDO330
4-70
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