CS52510-1
Typical Performance Characteristics: continued
Adjust Pin Current vs Temperature
Output Voltage Deviation (mV)
83.0
81.0
Adjust Pin Current (mA)
79.0
77.0
75.0
73.0
71.0
69.0
67.0
65.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0 160.0
Temperature (C)
Current Step Transient Response
100
50
0
-50
-100
C
OUT
=330mF
C
POWER
=110mF
C
CONTROL
=10mF
C
ADJUST
=25mF
V
CONTROL
=5V
V
POWER
=3.3V
V
OUT
=2.5V
Current (A)
7
0
0
0
1
2
3
Time (ms)
4
5
Application Notes
Theory of Operation
Design Guidelines
The CS52510-1 linear regulator provides adjustable voltages
from 1.25V to 5V at currents up to 10A. The regulator is pro-
tected against short circuits, and includes a thermal shut-
down circuit with hysteresis. The output, which is current
limited, consists of a PNP-NPN transistor pair and requires
an output capacitor for stability. A detailed procedure for
selecting this capacitor is included in the Stability
Considerations section.
V
POWER
Function
The CS52510-1 utilizes a two supply approach to maximize
efficiency. The collector of the power device is brought out to
the V
POWER
pin to minimize internal power dissipation
under high current loads.V
CONTROL
provides power for the
control circuitry and the drive for the output NPN transistor.
V
CONTROL
should be at least 1V greater than the output volt-
age. Special care has been taken to ensure that there are no
supply sequencing problems. The output voltage will not
turn on until both supplies are operating. If the control volt-
age comes up first, the output current will be typically limit-
ed to about 3mA until the power input voltage comes up. If
the power input voltage comes up first the output will not
turn on at all until the control voltage comes up. The output
can never come up unregulated.
The CS52510-1 can also be used as a single supply device
with the control and power inputs tied together. In this
mode, the dropout will be determined by the minimum con-
trol voltage.
Output Voltage Sensing
The CS52510-1 five terminal linear regulator includes a dedi-
cated Vsense function. This allows for true Kelvin sensing of
the output voltage. This feature can virtually eliminate errors
in the output voltage due to load regulation. Regulation will
be optimized at the point where the sense pin is tied to the
output.
Adjustable Operation
This LDO adjustable regulator has an output voltage range
of 1.25V to 5V. An external resistor divider sets the output
voltage as shown in Figure 1. The regulatorÕs voltage sensing
error amplifier maintains a fixed 1.253V reference between
the output pin and the adjust pin.
A resistor divider network R
1
and R
2
causes a fixed current
to flow to ground. This current creates a voltage across R
2
that adds to the 1.253V across R1 and sets the overall output
voltage. The adjust pin current (typically 50µA) also flows
through R
2
and adds a small error that should be taken into
account if precise adjustment of V
OUT
is necessary. The out-
put voltage is set according to the formula:
V
OUT
= 1.253V
´
R
1
+ R
2
R
1
+ R
2
´
I
ADJ
The term I
ADJ
´
R
2
represents the error added by the adjust
pin current.
R
1
is chosen so that the minimum load current is a least
10mA. R
1
and R
2
should be of the same composition for best
tracking over temperature. The divider resistors should be
placed as close to the load as possible.
V
CONTROL
V
OUT
CS52510-1
V
POWER
V
SENSE
Adjust
R1
R2
Figure 1: An external resistor divider sets the value of V
OUT
. The 1.253V
reference voltage drops across R1.
6
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
