Page 1
3.3 VOLT ULTRA LOW DROPOUT
REGULATOR
ISSUE 2 - MAY 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
2.7 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.
ZLDO330
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
•
Shutdown
Control
THERMAL
SHUTDOWN
SHUTDOWN
Low Battery Flag
LOW BATTERY
COMPARATOR
BIAS
CIRCUIT
Gnd
4-62
OUTPUT
DRIVE
BANDGAP
REFERENCE
Vin
Vo
Cs
Shaping
Page 2
ZLDO330
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
ELECTRICAL CHARACTERISTICS
TEST CONDITIONS (Unless otherwise stated) T
Parameter SYMBOL CONDITIONS MIN. TYP. MAX. UNITS
Output Current 300mA
Operating Temperature -40 to 85°C
Storage Temperature -55 to 150°C
Power Dissipation
(Tamb=25°C) 2W (Note 1)
=25°C,IL=10mA,Cs=10pF,C
amb
out
=1µF
Output voltage V
Output voltage
temperature coefficient
Line regulation
Load regulation
Dropout voltage
(Note3)
Quiescent current I
Quiescent current
at shutdown
Shutdown control
input
current
Shutdown control
threshold voltage
Output current in
shutdown mode
(Note4)
Output noise voltage
(Note4)
o
V
o
∆T
∆
V
o
∆
V
o
V
in-VoIL
q
I
qs
I
ins
V
ts
I
Ls
e
n
Vin=4.3V 3.2 3.3 3.4 V
Vin=4.3V
100 250 ppm/°C
(Note 2, Note 4)
Vin=4.3 to 20V 15 52 mV
IL=10 to 300mA
V
=4.3V
in
=10mA
I
=100mA
L
I
=300mA
L
45 78 mV
6
30
100
10
75
200
mV
Vin=4.3V, IL=0 0.56 1 mA
Vin=4.3V, IL=0,
V
shdn=Vin
V
=4.3V 2 10
shdn=Vin
11 30
µA
µA
Vin=4.3V
low(on)
0.4 V
high(off) 1.5
Vin=20V
V
=Gnd
o
Vin=4.3V
50 100 nA
190
µV RMS
f=10Hz to100kHz,
I
=100mA
L
Low battery detect
threshold
Low battery flag
output voltage
Low battery flag
leakage current
V
V
in(bld)
V
bl
I
bl
Ibl=100µA,
V
in<Vo
Vbl=6V,
V
in>Vo
+200mV
+400mV
4-63
out
0.2V
+
0.16 0.4 V
0.1 1
V
out
0.4V
+
V
µA
Page 3
ZLDO330
NOTES.
1. Maximum power dissipation of the device is calculated assuming the package is mounted on a PCB
measuring 2 inches square.
V
change x
O
2 Output voltage temperature coefficient is calculated as:-
V
x
temperature change
O
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
= V
at the nominal input V
+ 1V
in
out
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
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.
regulator.
1000000
measured
out
4-64
Page 4
TYPICAL CHARACTERISTICS
ZLDO330
1400
(out)
C
=1µF
1200
)
Ω
1000
800
600
400
Output Impedance (m
200
0
100
Frequency (Hz)
Output Impedance vs. Frequency
3.33
Io=10mA
V(in)=5V
3.32
3.31
3.30
3.29
Output Voltage (V)
3.28
3.27
-40
-20 0 20 6040 80
Temperature ( °C)
Output Voltage Temperature Coefficient
55
50
45
40
Ripple Rejection (dB)
35
30
25
20
15
10
5
0
100
1K 10K 100K
10pF
4.7pF
2.2pF
10K1K
100K
10pF
4.7pF
2.2pF
C(out)=1µF
Frequency (Hz)
Ripple Rejection vs. Frequency
680
640
600
A)
µ
560
520
480
440
Quiescent Current (
400
100
-40
0-20 20 40 60 80
Temperature ( °C)
V(in)=5V
Quiescent Current vs. Temperature
16
14
A)
µ
12
10
8
Shutdown Current (
6
-40
-20
08020 40 60
Temperature ( °C)
Shutdown Current vs. Temperature
V(in)=5V
3.61
3.60
3.59
3.58
3.57
3.56
L.B.F. Operation Voltage (V)
3.55
100
-40
-20 0 20 6040 80
V(in)=7V
Io=10mA
100
Temperature ( °C)
Low Battery Flag Operating Point
4-65
Page 5
ZLDO330
120
100
80
60
40
20
Dropout Voltage (mV)
0
0.1 1.0
Load Current (mA)
Dropout Voltage vs. Load Current
TYPICAL CHARACTERISTICS
85 °C
25 °C
-40 °C
0.8
0.4
0
Output Voltage Deviation (V)
10 100
1000
-0.4
0200
Line Transient Response
Output Voltage Deviation
400 600
Time (µs)
V
V
Io=100mA
800
(in)
=10V
(in)
=5V
1000
0.2
0
-0.2
Output Voltage Deviation (V)
-0.4
(in)
V
=5V
IO=0mA
Output Voltage Devi ation
040
80
Time (µs)
Load Transient Response
IO=100mA
SINGLE PULSE TEST T
1.0
0.1
amb
= 25 °C
0.1s
1s
DC
10ms
Load Current (AMPS)
120
160
200
0.01
2 5 10 201
Input-Output Differential Voltage (VOLTS)
Safe Operating Area
Operation in shaded area is not guaranteed
4-66
Page 6
+5V In +5V Out
C3
100nF
IC1
ZLDO330
LBF
SC
Vin
N/C
Spg
Gnd
D/C
Vout
C1
10pF
C2
1uF
+3.3V Out
0V Out0V In
Figure 1
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.
Voltage
Feedback
D1
ZLDO330
APPLICATIONS
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.
+ 5V Out
Switching
Regulator
Figure 2
ZLDO330
Spg
LBF
SC
Gnd
D/C
Vin
Vout
N/C
C1
10pF
C2
1uF
+ 3.3V Out
TR1
C4
220uF
D2
C5
220uF
0V Out
4-67
Page 7
ZLDO330
APPLICATIONS
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.
ZLDO330
Spg
LBF
SC
Gnd
D/C
Vin
Vout
N/C
4.8V
Figure 3
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.
C3
100nF
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.
C1
10pF
+3.3V
R1
C2
1uF
Microproc.
System
100k
Int errupt
Input
0V
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.
4-68
Page 8
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).
+5V
to 20V
Vin Vout
IC1
ZSR330
Gnd
Microproc .
System
Supply Input
IC2
ZLDO330
LBF
Spg
SC
Gnd
Vin
D/C
N/C
Vout
ZLDO330
APPLICATIONS
C1
10pF
+3.3V
0V
Figure 4
4-69
C3
100nF
C2
1uF
Switched
Output
0V
Page 9
ZLDO330
CONNECTION DIAGRAM
SM8 Package Suffix – T8
Top View –
Pin 6 must be left floating
SEE PIN DEFINITIONS
ORDERING INFORMATION
Part Number Package Part Mark
ZLDO330T8 SM8 ZLDO330
4-70
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