LND2950 / LND2951
Note 1: Output or reference voltage temperature coefficients is defined as the worst case voltage change divided by
the total temperature range.
Note 2: Unless otherwise specified all limits guaranteed for T
j
=25ºC, V
in
=V
o
+1V,I
L
=100µAand C
L
=1µF. Additional
conditions for the 8 pin versions are feedback tied to –XX V tap and output tied to output sense(V
out
=XX V) and V
shutdown
≤0.8
V.
Note 3: Regulations is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes
in output voltage due to heating effects are covered under the specification for thermal regulation.
Note 4: Line regulation for LND2951-xx is tested at 150ºCfor I
L
=1mA. For I
L =
100µA and Tj=125ºC, line regulation is
guaranteed by design to 0.2%. See typical performance characteristics for line regulation verse temperature and load
current.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV below its
nominal value measured at 1V differential. At very low values of programmed output voltage, the minimum input
supply voltage of 2V(2.3V over temperature) must be taken into account.
Note 6: V
ref
≤V
out
≤(Vin-1V),
2.3V
≤Vin ≤
30V,100µA≤I
L
≤
100mA,T
J
≤T
JMAX
Note 7: Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the
total temperature range.
Note 8: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the
nominal reference voltage measured at V
O
+1V input. To express these thresholds in terms of output voltage change,
multiply by the error amplifier gain =V
out
/V
ref
=(R1+R2)/R2. For example, at a programmed output voltage of 5V, the
error output is guaranteed to go low when the output drops by 95mVx5V/1.235V=384mV. Thresholds remain constant
as a percent of V
out
as V
out
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5%
guaranteed.
Note 9: V
shutdown
≥
2V,Vin
≤30V,V
out
=0, Feed-back pin tied to –XX V tap.
APPLICATION HINTS
External Capacitors
A 1.0
µF
(or greater ) capacitor is required between the output and the ground for stability at output
voltages of 5V or more. At lower output voltages, more capacitance is required. 2.2
µF
or more is
recommended for 3 V and 3.3 V versions.
Programming the Output Voltage
The LND2951 may be pin-strapped for the nominal fixed output voltage. Alternatively it may be
programmed for any output voltage between 1.24 V and 29 V depending upon the requirements.
BLOCK DIAGRAM AND TYPICAL APPLICATIONS
Unregulated DC
+
Unregulated DC
7
FEEDBACK
INPUT
8
1
OUTPUT
2
OUTPUT
Vout
I <= 100mA
L
+
-
ERROR
AMPLIFIER
+
See
Application
Hints
From
CMOS
or
TTL
3
SHUTDOWN
+
+
60 mV
+
1.23 V
Reference
+
Vout
I <= 100mA
L
INPUT
SENSE
+
See
Application
Hints
+
-
6
ERROR
AMPLIFIER
XX VTAP
330k
Ω
5
II
60k
ERROR
-
+
1.23 V
Reference
To
CMOS
or
TTL
4
GROUND
Error detection Comparator
GROUND
•
Linear Dimensions, Inc.
•
445 East Ohio Street, Chicago IL 60611 USA
•
tel 312.321.1810
•
fax 312.321.1830
•
•
LINEAR_DIMENSIONS [ LINEAR DIMENSIONS SEMICONDUCTOR ]
