User manual

page 60
Analog System Lab Kit PRO
experiment 11
The ASLK Pro kit includes an on-board voltage regulator evaluation module
TPS7250. The goal of this experiment is to study the parameters of the
Low Dropout Regulator (LDO) IC TPS7250 from Texas Instruments using
the on-board evaluation module.
TPS7250 evaluation module helps us evaluate the operation and performance of
the TPS7250 family of linear regulators. The linear regulator TPS7250 from Texas
Instrumentsiscapableof200mAoutputcurrentat5Vxedoutputvoltagelevel.
It is a low quiescent current, low noise, high PSRR, fast start-up LDO with excellent
line and transient response. See Figure 11.1 for the schematic diagram of the
evaluation module.
The input supply voltage VIN is fed at screw terminal CN3 and falls in the range
5.5V to 11V. The leads to the input supply must be as short as possible and must
be twisted to reduce EMI transmission. The capacitor C102 improves the transient
response of the regulator. The capacitor C101 helps to reduce the ringing on input
when supply wires are too long.
To study the parameters (Line regulation, Load regulation) of LDO TPS7250 using the
on-board evaluation module.
11.1 Brief theory and motivation
11.2Specications
11.3 Measurements to be taken
Goal of the experiment
Obtain the Line Regulation: Vary the input voltage (from 5.5V to 11V in steps of
0.5V)andplottheoutputvoltageasthefunctionoftheinputvoltageforaxed
output load.
Obtain the Load Regulation: Vary the load (within the permissible limits) such that
loadcurrentvariesandobtaintheoutputvoltageforaxedinputvoltage.Plot
the output voltage as function of the load current.
1
2
Figure 11.1: Schematic diagram of on-board evaluation module
The regulator can be enabled/disabled using the ON/OFF jumper JP7. The “Enable”
pin(EN)mustneverbeleftoating.Connectingashortingjumperwirebetweenpins
1 (GND) and pin 2 (EN) of JP7 enables the regulator. Connecting a jumper wire between
pins 2 (EN) and pin 3 (VIN) disables the regulator. Output voltage is available on screw
terminal CN4, or Vout pin header, and the typical load current is 200mA.
VIN 5.5 -10 V VOUT 5
V
GND
3
IN
5
IN
6
EN
4
OUT
7
OUT
8
SENSE
1
PG
2
TPS7250
SENSE
PG
GND
EN
OUT
OUT
IN
IN
IC1
IN
OUT
ENABLE
REG IN
HD117
VIN
HD118
VOUT
HD116
GND
R4
4K7
OUT
CN3
VIN
CN4
VOUT
JP6
VCC+10
R101
247K
C101
1u F
C102
100nF
C103
10uF
JP7
GND
GND
LD4
@250mA
ON
OFF