SIP32467 Datasheet, PDF (11/13 Pages) Vishay Siliconix – 50 mΩ, Slew Rate Controlled Load Switch in WCSP

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DETAILED DESCRIPTION
SiP32467 and SiP32468 are high side, slew rate controlled,
load switches. They incorporate a negative charge pump at
the gate to keep the gate to source voltage high when
turned on. This keeps the on resistance low at lower input
voltages. SiP32467 and SiP32468 are designed with slow
slew rate to minimize the inrush current during turn on.
These devices have a reverse blocking circuit, when
disabled, to prevent the current from going back to the input
when the output voltage is higher than the input voltage. The
SiP32467 can be used as a bi-directional switch and can be
turned ON and OFF when power is at either IN or OUT. The
SiP32468 has an output pull down resistor to discharge the
output capacitance when the device is off.
APPLICATION INFORMATION
Input Capacitor
While a bypass capacitor on the input is not required, a
4.7 μF or larger capacitor for C_IN is recommended in almost
all applications. The bypass capacitor should be placed as
physically close as possible to the input pin to be effective
in minimizing transients on the input. Ceramic capacitors are
recommended over tantalum because of their ability to
withstand input current surges from low impedance sources
such as batteries in portable devices.
Output Capacitor
A 0.1 μF capacitor across V_OUT and GND is recommended
to insure proper slew operation. There is inrush current
through the output MOSFET and the magnitude of the
inrush current depends on the output capacitor, the bigger
the C_OUT the higher the inrush current. There are no ESR or
capacitor type requirement.
Enable
The EN pin is compatible with CMOS logic voltage levels. It
requires at least 1 V or above to fully shut down the device
and 0.4 V or below to fully turn on the device. There is a
2.6 MΩ resistor connected between EN pin and IN pin.
Protection Against Reverse Voltage Condition
This device contains a reverse blocking circuit. When
disabled (V_EN greater than 1 V) this circuit keeps the output
current from flowing back to the input when the output
voltage is higher than the input voltage.
Thermal Considerations
Due to physical limitations of the layout and assembly of the
device the maximum switch current is 1.2 A as stated in the
Absolute Maximum Ratings table. However, another limiting
SiP32467, SiP32468
Vishay Siliconix
characteristic for the safe operating load current is the
thermal power dissipation of the package.
The maximum power dissipation in any application
is dependant on the maximum junction temperature,
T_J(max.) = 125 °C, the junction-to-ambient thermal
resistance, θ_J-A = 205 °C/W, and the ambient temperature,
T_A, which may be expressed as:
P (max.) = ^{TJ (max.) - TA}
θ_{J- A}
= ^{125 - TA}
205
It then follows that, assuming an ambient temperature of
70 °C, the maximum power dissipation will be limited to
about 268 mW.
So long as the load current is below the 1.2 A limit, the
maximum continuous switch current becomes a function
two things: the package power dissipation and the R_DS(ON)
at the ambient temperature.
As an example let us calculate the worst case maximum
load current at T_A = 70 °C. The worst case R_DS(ON) at 25 °C
is 120 mΩ at V_IN = 1.5 V. The R_DS(ON) at 70 °C can be
extrapolated from this data using the following formula:
R_DS(ON) (at 70 °C) = R_DS(ON) (at 25 °C) x (1 + T_C x ΔT)
Where T_C is 2800 ppm/°C. Continuing with the calculation
we have
R_DS(ON) (at 70 °C) = 120 mΩ x (1 + 0.0028 x (70 °C - 25 °C))
= 135 mΩ
The maximum current limit is then determined by
I _LOAD (max.) <
P (max.)
R _DS(ON)
which in this case is 1.99 A. Under the stated input voltage
condition, if the 1.99 A current limit is exceeded the internal
die temperature will rise and eventually, possibly damage
the device.
To avoid possible permanent damage to the device and
keep a reasonable design margin, it is recommended to
operate the device maximum up to 1.2 A only as listed in the
Absolute Maximum Ratings table.
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon
Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and
reliability data, see www.vishay.com/ppg?67757
S14-0843-Rev. B, 28-Apr-14
11
Document Number: 67757
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