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Datasheet: ZLDO485TB (Zetex Semiconductors)

Low Dropout Regulator

 

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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 4.85 volts.
The ZLDO485 consumes a typical quiescent
current of only 1mA 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
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 11
A.
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
4.85 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
4.85 VOLT ULTRA LOW DROPOUT
REGULATOR
ISSUE 2 - MAY 1997
LOW BATTERY
COMPARATOR
Low Battery Flag
Vin
OUTPUT
DRIVE
BIAS
CIRCUIT
SHUTDOWN
THERMAL
SHUTDOWN
Shutdown
Control
BANDGAP
REFERENCE
Vo
Shaping
Gnd
Cs
ZLDO485
4-71
ZLDO485
ABSOLUTE MAXIMUM RATING
Input Supply
Voltage Range
-0.3 to 20V
Shutdown Input
Voltage Range
-0.3 to V
in
Low Battery Output
Voltage Range
-0.3 to 20V
Output Current
300mA
Operating Temperature
-40 to 85C
Storage Temperature
-55 to 150C
Power Dissipation
(T
amb
=25C)
2W (Note 1)
Parameter
SYMBOL
CONDITIONS
MIN.
TYP.
MAX. UNITS
Output voltage
V
o
V
in
=5.85V
4.75
4.85
4.95
V
Output voltage
temperature coefficient
V
o
T
V
in
=5.85V
(Note 2, Note 4)
100
250
ppm/C
Line regulation
V
o
V
in
=5.85 to 20V
20
69
mV/V
Load regulation
V
o
I
L
=10 to 300mA
V
in
=5.85V
68
119
mV
Dropout voltage
(Note3)
V
in
-V
o
I
L
=10mA
I
L
=100mA
I
L
=300mA
6
30
100
10
75
200
mV
Quiescent current
I
q
V
in
=5.85V, I
L
=0
0.63
1
mA
Quiescent current
at shutdown
I
qs
V
in
=5.85V, I
L
=0,
V
shdn
=V
in
11
30
A
Shutdown control input
current
I
ins
V
shdn
=V
in
=5.85V
2
10
A
Shutdown control
threshold voltage
V
ts
V
in
=5.85V
low(on)
high(off)
1.5
0.4
V
Output current in
shutdown mode
(Note4)
I
Ls
V
in
=20V
V
o
=Gnd
50
100
nA
Output noise voltage
(Note4)
e
n
V
in
=5.85V
f=10Hz
to100kHz,
I
L
=100mA
190
V RMS
Low battery detect
voltage
V
in(bld)
V
o
+
0.2V
Vo +
0.4V
V
Low battery flag
output voltage
V
bl
I
bl
=100
A,
V
in
<V
o
+200mV
0.16
0.4
V
Low battery flag
leakage current
I
bl
V
bl
=6V,
V
in
>V
o
+400mV
0.1
1
A
ELECTRICAL CHARACTERISTICS
TEST CONDITIONS (Unless otherwise stated) T
amb
=25C,I
L
=10mA,C
s
=10pF,C
out
=1
F
4-72
ZLDO485
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 11
A (typ). A precision bandgap
reference gives
2.5% output tolerance and
good temperature characteristics over the range
-40 to +85C. 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.
4-73
ZLDO485
Frequency (Hz)
Output Impedance vs. Frequency
O
u
t
pu
t
I
m
pe
da
n
c
e
(
m
)
100
1K
10K
100K
200
600
400
800
1000
1200
10pF
4.7pF
2.2pF
Sh
u
t
do
w
n
C
u
r
r
e
n
t
(
A)
Shutdown Current vs. Temperature
Temperature ( C)
-40
-20
0
100
6
10
12
14
16
18
8
Out
p
u
t
V
o
lt
a
g
e
(
V
)
Temperature ( C)
Output Voltage Temperature Coefficient
-40
0
40
80
4.83
4.85
4.87
4.89
Frequency (Hz)
Ripple Rejection vs. Frequency
R
i
ppl
e
R
e
j
e
c
t
i
on (
d
B
)
100
1K
10K
100K
5
10
15
20
25
30
35
40
45
-20
20
60
Io= 10mA
C
(out)
= 1
F
10pF
4.7pF
2.2pF
100
4.84
4.82
4.86
4.88
Q
u
i
e
s
c
en
t
C
u
rr
e
n
t

(
A)
Temperature ( C)
Quiescent Current vs. Temperature
L
.
B
.
F
.
Ope
r
a
t
i
on
V
o
lt
a
g
e
(
V
)
Temperature ( C)
Low Battery Flag Operating Point
700
680
660
640
620
600
580
540
-40
-20
0
100
5.12
5.10
5.09
5.14
5.15
5.13
5.11
-40
-20
0
100
720
560
20
40
60
80
20
40
60
80
20
40
60
80
V
(in)
= 7V
V
(in)
= 7V
1400
1600
1800
0
C
(out)
= 1
F
V
(in)
= 7V
Io= 10mA
V
(in)
= 7V
TYPICAL CHARACTERISTICS
4-74
ZLDO485
D
r
o
p
ou
t
V
o
l
tage
(mV
)
180
160
140
120
100
80
60
40
20
0
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 (
s)
Line Transient Response
0
200
400
600
800
1000
-1
0
1
Ou
t
p
u
t
V
o
l
t
a
g
e D
evi
atio
n

(V
)
Ou
tpu
t V
o
l
tage D
e
v
i
ati
on

(
V
)
0.5
0
-0.5
Io=0mA
Io=100mA
V(in)=7V
0
200
400
600
800
1000
Time (
s)
Load Transient Response
Output Voltage Deviation
Output Voltage Deviation
Safe Operating Area
SINGLE PULSE TEST T
amb
=25
C
1.0
0.1
0.01
L
o
ad

C
u
rre
n
t
(
A
)
Input-Output Differential Voltage (V)
2
5
10
20
1
DC
DC
1s
0.1s
10ms
TYPICAL CHARACTERISTICS
Operation in shaded area is not guaranteed
4-75
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