Texas Instruments TPS70151 Series, User Manual, Page: 17 / 28

Adjustment Through Component Changes
2-3 EVM Adjustments and Test Points
2.2 Adjustment Through Component Changes
Through minor soldering work, the DUT can be changed to any of the fixed-
voltage members of the TPS701xx LDO family. In addition, Table 2–2 summa-
rizes the most common components which a user might wish to replace in or-
der to more fully characterize the LDO.
Table 2–2. Commonly Changed Components
Component Regulator 1 Regulator 2 EVM Value
Input capacitor C2 C3 100
µ
F
Output capacitor C12 C13 33
µ
F
Resistors controlling transient pulse generator pulse width and
duty cycle (see Table 2-3) R1, R2 R1, R2 4.3 k
Ω
,
10 k
Ω
Resistor controlling load transient rise time
†
R6 R8 510
Ω
† Larger resistance slows rise time.
Table 2–3 gives the equations for computing the resistor sizes necessary for
changing the transient pulse width and/or duty cycle.
Table 2–3. Timing Equations
Timing Equations With Diode D1 for
Low Duty Cycles Timing Equations Without Diode D1
R1
+
t
on
0.693
C
R1
+
t
on
(2D
*
1)
0.693
D C
R2
+
t
on
(1
*
D)
0.693 D C
R2
+
t
on
(1
*
D)
0.693 D C
Note: ton = desired load on-time [s]
D = on-time duty cycle
C = total capacitance in circuit (1 uF)
RH1, RH2 = Timer resistors value (refer to schematics) [
Ω
]
2.3 Test Setup
Figure 2–1 shows the test setup. Follow these steps for initial power up of the
SLVP152
1) Adjust the settings of jumpers to fit test requirements (see jumper func-
tions in Table 2-1). Verify that the switch controlling the load transient gen-
erator is off, no external load is connected through J3 and that JP5 and JP6
are open to prevent loading through the onboard resistors.
2) Connect a 12-V lab power supply to the V
CC
input and GND at J2. The po-
larity is printed on the board. A current limit of 100 mA should be adequate
for the test and measure circuit.
3) Connect a second lab power supply (at least capable of supplying 2 A) to
the J1 connector at V
IN1
, V
IN2
, GND1 and GND2. The polarity is printed
on the board. Verify that the lab power supply output voltage limit is set to
6 V and that the output is set to 0 V.
4) Turn on the 12-V lab supply. Turn on the second power supply and ramp
the input voltage up to the desired maximum but not higher than 6 V.