Datasheet

ADP190/ADP191 Data Sheet
Rev. E | Page 12 of 16
The turn-off time is defined as the delta between the time from
90% to 10% of VOUT reaching its final value. It is also dependent
on the RC time constant.
The ADP191 incorporates an internal output discharge resistor
to discharge the output capacitance when the ADP191 output is
disabled. See Figure 28 and Figure 29 for a comparison of turn-
off times.
2
CH1 1V
CH2 500mV
M10µs A CH1 1V
T 30.36µs
1
T
V
OUT
= 1.8V
V
EN
= 3.6V
I
LOAD
= 200mA,
C
LOAD
= 1µF
I
LOAD
= 100mA,
C
LOAD
= 1µF
I
LOAD
= 100mA,
C
LOAD
= 4.7µF
V
EN
07874-020
Figure 28. ADP190 Typical Turn-Off Time, Various Load Currents
3
CH1 2.00V
CH3 500mV
M200µs
A CH1 600mV
T 10.20%
1
V
EN
V
OUT
T
07874-129
Figure 29. ADP191 Typical Turn-Off Time, Load Current = 0 mA
THERMAL CONSIDERATIONS
In most applications, the ADP190/ADP191 do not dissipate
much heat due to their low on-channel resistance. However, in
applications with high ambient temperature and load current,
the heat dissipated in the package can be large enough to cause
the junction temperature of the die to exceed the maximum
junction temperature of 125°C.
The junction temperature of the die is the sum of the ambient
temperature of the environment and the temperature rise of the
package due to the power dissipation, as shown in Equation 1.
To guarantee reliable operation, the junction temperature of
the ADP190/ADP191 must not exceed 125°C. To ensure that
the junction temperature stays below this maximum value, the
user must be aware of the parameters that contribute to junction
temperature changes. These parameters include ambient temper-
ature, power dissipation in the power device, and thermal
resistances between the junction and ambient air (θ
JA
). The θ
JA
value is dependent on the package assembly compounds that
are used and the amount of copper used to solder the package
GND pin to the PCB. Table 6 shows typical θ
JA
values of the 4-ball
WLCSP for various PCB copper sizes. Table 7 shows the typical
Ψ
JB
value of the 4-ball WLCSP.
Table 6. Typical θ
JA
Values for WLCSP
Copper Size (mm
2
) θ
JA
(°C/W)
0
1
260
50 159
100 157
300 153
500 151
1
Device soldered to minimum size pin traces.
Table 7. Typical Ψ
JB
Values
Package Ψ
JB
Unit
4-Ball WLCSP 58.4 °C/W
The junction temperature of the ADP190/ADP191 can be
calculated from the following equation:
T
J
= T
A
+ (P
D
× θ
JA
) (1)
where:
T
A
is the ambient temperature.
P
D
is the power dissipation in the die, given by
P
D
= [(V
IN
− V
OUT
) × I
LOAD
] + (V
IN
× I
GND
) (2)
where:
I
LOAD
is the load current.
I
GND
is the ground current.
V
IN
and V
OUT
are the input and output voltages, respectively.
Power dissipation due to ground current is quite small and
can be ignored. Therefore, the junction temperature equation
simplifies to the following:
T
J
= T
A
+ {[(V
IN
− V
OUT
) × I
LOAD
] × θ
JA
} (3)
As shown in Equation 3, for a given ambient temperature, input-
to-output voltage differential, and continuous load current, there
exists a minimum copper size requirement for the PCB to ensure
that the junction temperature does not rise above 125°C. Figure 30
to Figure 35 show junction temperature calculations for different
ambient temperatures, load currents, V
IN
to V
OUT
differentials,
and areas of PCB copper.