SI91871DMP-18-E3 Vishay, SI91871DMP-18-E3 Datasheet - Page 9

• Manufacturer Part Number: SI91871DMP-18-E3
• Description: IC LDO REG 1.8V 500MA MLP33-5
• Manufacturer: Vishay

Specifications of SI91871DMP-18-E3

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.8V
• Voltage - Input: 2 V ~ 6 V
• Voltage - Dropout (typical): 0.13V @ 300mA
• Number Of Regulators: *
• Current - Output: 300mA
• Current - Limit (min): 500mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: *
• Package / Case: *
• Number Of Outputs: 1
• Polarity: Positive
• Input Voltage Max: 6 V
• Output Voltage: 1.8 V
• Output Type: Fixed
• Dropout Voltage (max): 0.1 V at 50 mA
• Output Current: 300 mA
• Line Regulation: 20 mV
• Load Regulation: 20 mV
• Voltage Regulation Accuracy: 2 %
• Maximum Power Dissipation: 2.3 W
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DETAILED DESCRIPTION
The Si91871 is a low-noise, low drop-out and low quiescent
current linear voltage regulator, packaged in a small footprint
MLP33-5 package. The Si91871 can supply loads up to
300 mA. As shown in the block diagram, the circuit consists of
a bandgap reference error, amplifier, p-channel pass transistor
and feedback resistor string. An external bypass capacitor
connected to the BP pin reduces noise at the output.
Additional blocks, not shown in the block diagram, include a
precise current limiter, reverse battery and current protection
and thermal sensor.
Thermal Overload Protection
The thermal overload protection limits the total power
dissipation and protects the device from being damaged.
When the junction temperature exceeds 150_C, the device
turns the p-channel pass transistor off.
Reverse Battery Protection
The Si91871 has a battery reverse protection circuitry that
disconnects the internal circuitry when V
GND voltage. There is no current drawn in such an event.
When the SD pin is hardwired to V
the SD pin to V
protection is desired. Hardwiring the SD pin directly to the V
pin is allowed when reverse battery protection is not desired.
Noise Reduction
An external 10-nF bypass capacitor at BP is used to create a
low pass filter for noise reduction. The start-up time is fast,
since a power-on circuit pre-charges the bypass capacitor.
After the power-up sequence the pre-charge circuit is switched
to standby mode in order to save current. It is therefore not
recommended to use larger bypass capacitor values than
50 nF. When the circuit is used without a capacitor, stable
operation is guaranteed.
Auto-Discharge
The Si91871 V
to ground when the SD pin is low.
Stability
The circuit is stable with only a small output capacitor equal to
6 nF/mA (= 2 mF @ 300 mA). Since the bandwidth of the error
amplifier is around 1−3 MHz and the dominant pole is at the
output node, the capacitor should be capacitive in this range,
i.e., for 150-mA load current, an ESR <0.2 W is necessary.
Parasitic inductance of about 10 nH can be tolerated.
Safe Operating Area
The ability of the Si91871 to supply current is ultimately
dependent on the junction temperature of the pass device.
Junction temperature is in turn dependent on power
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.
http://www.vishay.com/ppg?72012.
Document Number: 72012
S-51147—Rev. F, 20-Jun-05
OUT
IN
has an internal 100-W (typ.) discharge path
via a 100-kW resistor if reverse battery
IN
, the user must connect
IN
drops below the
For related documents such as package/tape drawings, part marking, and reliability data, see
IN
dissipation in the pass device, the thermal resistance of the
package and the circuit board, and the ambient temperature.
The power dissipation is defined as
Junction temperature is defined as
To calculate the limits of performance, these equations must
be rewritten.
Allowable power dissipation is calculated using the equation
While allowable output current is calculated using the equation
Ratings of the Si91871 that must be observed are
T
Rθ
The value of Rθ
value of Rθ
approximately 46 _C/W.
Figure 1 shows the performance limits graphically for the
Si91871 mounted on the circuit board used for thermal
characterization.
Jmax
JC
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
= 8 _C/W.
= 125 _C, T
P
T
P
I
OUT
J
D
D
0
= T
= (V
= (T
CA
= (T
A
for the board used in device characterization is
J
(V
IN
+ ((P
CA
1
− T
J
IN
– V
− T
Figure 1. Safe Operating Area
Amax
− V
A
is dependent on the PC board used. The
D
OUT
A
)/ (Rθ
OUT
* (Rθ
)/ (Rθ
= 85 _C, (V
2
)
) * I
MAX
V
JC
IN
JC
OUT
JC
= 5.3 V
− V
+ Rθ
+ Rθ
3
+ Rθ
OUT
.
Vishay Siliconix
CA
CA
IN
(V)
CA
)
)).
– V
4
) * (V
OUT
IN
)
max
5
Si91871
– V
www.vishay.com
OUT
= 5.3 V,
T
T
T
A
A
A
= 50_C
= 70_C
= 85_C
6
).
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