US1205
300 mA LOW DROPOUT POSITIVE
ADJUSTABLE REGULATOR
PRELIMINARY DATASHEET
FEATURES
SOT23 package
Stable with 2.2uF ceramic capacitor
1% Voltage Reference Accuracy
Only 270mV Dropout at 300 mA
170mV Dropout at 150mA
10nA Quiescent Current in Shutdown
Current Limit and Thermal Shutdown
Logic input Enable pin
DESCRIPTION
The US1205 device is an efficient linear voltage regula-
tor with better than 1% initial voltage accuracy, very low
dropout voltage and very low ground current designed
especially for hand held, battery powered applications.
Other features of the device are; TTL compatible enable/
shutdown control input, current limiting and thermal
shutdown.
The US1205 is available in fixed and adjustable output
voltage versions in a small SOT23-5 package.
APPLICATIONS
Laptop, Notebook & Palmtop computers
Battery powered Equipments
PCMCIA Vcc & Vpp regulator
Concumer Electronics
High Efficiency Linear Power Supplies
TYPICAL APPLICATION
Vin
C1
2.2uF
1
Vin
2
Gnd
Vout
5
R1
C2
2.2uF
Vout
Vo=1.242
X
(1+R1/R2)
R2
S.D.
Enable
3
En
Adj
4
1205app1-1.1
Typical application of the US1205 ajustable.
3.3V
C1
2.2uF
1
Vin
2
Gnd
3
En
Vout
5
C2
2.2uF
2.5V
S.D.
Enable
Byp
4
C3
1000pF
1205app2-1.2
Typical application of the US1205 Fixed voltage.
PACKAGE ORDER INFORMATION
Tj (°C)
0 TO 125
0 TO 125
0 TO 125
0 TO 125
0 TO 125
Rev. 1.4
9/25/00
5 LEAD
SOT 23
US1205CL
US1205-25CL
US1205-30CL
US1205-33CL
US1205-36CL
SOT23
Marking
AT00
AT25
AT30
AT33
AT36
Output
Voltage
Adj
2.5 V
3.0 V
3.3 V
3.6 V
2-1
US1205
ABSOLUTE MAXIMUM RATINGS
Input Voltage (Vin) ............................................................. 10V
Enable Input Voltage ........................................................... 10V
Storage Temperature Range ................................ -65°C TO 150°C
Operating Junction Temperature Range ...................... 0°C TO 150°C
PACKAGE INFORMATION
5 PIN SOT23 ( L ) Adjustable
En Gnd Vin
3
2
1
5 PIN SOT23 ( L ) Fixed
En Gnd Vin
3
2
1
AT00
4
5
θ
JA
=220°C/W
4
ATxx
5
θ
JA
=220°C/W
Adj
Vout
Byp
Vout
ELECTRICAL SPECIFICATIONS
Unless otherwise specified ,these specifications apply over ,Cin=Co=22uF, Io=100uA, Vinmin=2.5V(Adjustable
devices) Vin=Vo+1V(for fixed voltage devices), Vout=Vfb (for adjustable version only), Cbyp=470pF(for fixed output
versions only), Venb=2V and Ta=25°C. Typical values refer to Ta=25
°C.Low
duty cycle pulse testing are used
which keeps junction and case temperatures equal to the ambient temperature.
PARAMETER
SYM TEST CONDITION
MIN
TYP MAX
UNITS
Reference Voltage
Vo
-1
1
%
See Table 1 for typical values
(Note 4)
-2
2
Line Regulation
dVi
Vo+1V<Vin<10
0.005
%/V
Load Regulation (note 1)
dVL
1mA<Io<100mA
0.8
%
100mA<Io<300mA
0.1
%
Dropout Voltage (note 2)
dVio
Io=100uA
10
50
mV
Io=100uA (Note 4)
13
70
mV
Io=50mA
85
110
mV
Io=50mA (Note 4)
100
140
mV
Io=150mA
170
220
mV
Io=150mA (Note 4)
204
260
mV
Io=300mA
270
350
mV
Io=300mA (Note 4)
324
400
mV
Ground Current (Note 3)
Iq
Ven=2V, Io=100uA
120
160
uA
Io=100uA (Note 4)
240
uA
Io=50mA
420
600
uA
Io=50mA (Note 4)
540
uA
Io=150mA
2200 2900
uA
Io=150mA (Note 4)
2900
uA
Io=300mA
7200 9500
uA
Io=300mA (Note 4)
9300
uA
Ground Current-S.D Activated Iqsd
S.D pin<0.1V
0.1
uA
S.D pin=0.8V
8
Current Limit
Icl
Vo=0V
320
420
mA
Thermal Regulation
dVp
Vin=10V, Io=150mA,10 mS PULSE
0.05
%/W
Adjust Pin Current
Iadj
Vin=2.5V,Vo=Vadj
0.1
uA
Enable pin input LO voltage
Venl
Regulator OFF
0.8
V
Enable pin input HI voltage
Venh Regulator ON
2
V
Enable pin input LO current
Venl=0V to 0.8V
0.01
uA
Enable pin input HI current
Venh=2V to Vin
20
uA
2-2
Rev. 1.4
9/25/00
US1205
Note 1 :
Low duty cycle pulse testing with Kelvin con-
nections are required in order to maintain accurate data.
Note 2 :
Drop-out voltage is defined as the minimum
differential voltage between Vin and Vout required to main-
tain regulation at Vout. It is measured when the output
voltage drops 1% below its nominal value.
Note 3
: Ground current is the the regulator quiescent
current plus the pass transistor current. The total cur-
rent from the supply is the sum of the load current plus
the ground pin current.
Note 4
: The specification applies for the junction tem-
perature of 0 to +125°C.
Pin DescRIPTIONS
PIN #
4
4
5
PIN SYMBOL
Adj
(Adjustable only)
Byp
(Fixed output only)
Vout
PIN DESCRIPTION
A resistor divider from this pin to the Vout pin and ground sets
the output voltage.
A 470 to 1000pF bypass capacitor connected to this pin re-
duces the output noise.
The output of the regulator .A minimum of 2.2uF with max
ESR of 1 ohm capacitor must be connected from this pin to
ground to insure stability.
Ground pin. This pin must be connected to the lowest poten-
tial in the system & all other pins must be at higher potential
with respect to this pin.
Enable pin. A low signal or left open on this pin shuts down the
output.This pin must be tied HI or to Vin for normal operation.
The input pin of the regulator. Typically a large storage capacitor
is connected from this pin to ground to insure that the input
voltage does not sag below the minimumdrop out voltage dur-
ing the load transient response. This pin must always be higher
than Vout by at least the amount of the dropout voltage and
some margin in order for the device to regulate properly.
2
GND
3
1
En
Vin
5 LEAD
SOT 23
US1205
US1205-25
US1205-30
US1205-33
US1205-36
Output
Voltage
1.242V
2.5 V
3.0 V
3.3 V
3.6 V
The output voltage of the adjustable device can be set using:
Vo=1.242
X
(1+R1/R2)
Where;
R1=Resistor connected from output to the Adj pin
R2=Resistor connected from Adj pin to GND
Table 1- Nominal output voltage v.s. part number
BLOCK DIAGRAM
Vin
Vout
Vin
Vout
Adj
THERMAL
SHUTDOWN
Byp
1.242V
+
1.242V
+
THERMAL
SHUTDOWN
Gnd
1205blk1-1.1
En
Gnd
1205blk2-1.0
En
Figure 1- US1205 Adjustable block diagram
Rev. 1.4
9/25/00
Figure 2- US1205 Fixed output block diagram
2-3
嵌入式系统
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