CS5253-1GDPR5 Cherry Semiconductor Corporation, CS5253-1GDPR5 Datasheet - Page 6

• Manufacturer Part Number: CS5253-1GDPR5
• Description: 3A LDO 5-Pin Adjustable Linear Regulator
• Manufacturer: Cherry Semiconductor Corporation

The CS5253-1 linear regulator provides adjustable voltages
from 1.26V to 5V at currents up to 3A. 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
The CS5253-1 utilizes a two supply approach to maximize
efficiency. The collector of the power device is brought out
to the V
under high current loads. V
trol circuitry and the drive for the output NPN transistor.
V
voltage. 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
voltage comes up first, the output current will be limited to
about three milliamperes 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 CS5253-1 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
control voltage.
Output Voltage Sensing
The CS5253-1 five terminal linear regulator includes a ded-
icated V
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.
CONTROL
POWER
V
30
25
20
15
10
POWER
5
0
0
POWER
SENSE
Function
V
CONTROL
should be at least 1V greater than the output
Only Output Current vs Junction Temperature
20
V
POWER
V
function. This allows for true Kelvin sensing
pin to minimize internal power dissipation
OUT
not connected
= 0V
= 6V
40
Theory of Operation
Junction Temperature (C)
60
CONTROL
80
Typical Performance Characteristics: Continued
provides for the con-
100
120
140
6
Adjustable Operation
This LDO adjustable regulator has an output voltage range
of 1.26V to 5V. An external resistor divider sets the output
voltage as shown in Figure 1. The regulatorÕs voltage sens-
ing error amplifier maintains a fixed 1.260V reference
between the output pin and the adjust pin.
A resistor divider network R
to flow to ground. This current creates a voltage across R
that adds to the 1.260V across R
put voltage. The adjust pin current (typically 50µA) also
flows through R
taken into account if precise adjustment of V
sary. The output voltage is set according to the formula:
The term I
pin current. R
is at least 10mA. R
tion for best tracking over temperature. The divider resis-
tors should be placed physically as close to the load as pos-
sible.
Figure 1: Typical application schematic. The resistor divider sets V
with the internal 1.260V reference dropped across R1.
5V
40
35
30
25
20
15
10
V
5
0
0
CONTROL
ADJ
V
3.3V
20
OUT
1
´ R
is chosen so that the minimum load current
Supply Current vs Junction Temperature
2
2
and adds a small error that should be
= 1.260V ´
1
represents the error added by the adjust
and R
40
Design Guidelines
Junction Temperature (C)
V
V
CONTROL
POWER
2
CS5253-1
Adjust
60
should be of the same composi-
1
R
V
and R
1
SENSE
R
V
1
+R
OUT
1
and sets the overall out-
80
2
2
+ R
I
OUT
causes a fixed current
R1
R2
I
V
I
V
OUT
2
= 100mA
OUT
100
CONTROL
POWER
´ I
= 3A
= 1A
ADJ
OUT
= 2.05V
120
@3A
= 2.75V
2.5V
is neces-
140
OUT
2
,