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UP7706

UP7706U8, uP7706 / 3A Ultra Low Dropout Linear Regulator

Unspecified 

uP7706

Application Information

The uP7706 is a high performance linear regulator

specifically designed to deliver up to 3A output current with

very low input voltage and ultra low dropout voltage. With

dual-supply configuration, the uP7706 operates with a wide

input voltage VIN range from 1.0V to 5.5V and is ideal for

applications where VOUT is very close to VIN .

Supply Voltage for Control Circuit VCNTL

Unlike other linear regulators that use a P-Channel

MOSFET as the pass transistor, the uP7706 uses an N-

Channel as the pass transistor. N-Channel MOSFET

provides lower on-resistance and better stability meeting

stringent requirements of current generation

microprocessors and other sensitive electronic devices.

The drain of N-Channel MOSFET is connected to VIN and

the source is connected to VOUT. This requires that the

supply voltage VCNTL for control circuit is at least 1.5V higher

than the output voltage to provide enough overdrive capability

for the pass transistor thus to achieve low dropout and fast

transient response. It is highly recommended to bias the

device with 5V voltage source if available.

Use a minimum 0.1uF ceramic capacitor plus a 10Ω

resistor to locally bypass the control voltage.

Input/Output Capacitor Selection

The uP7706 has a fast transient response that allows it to

handle large load changes associated with high current

applications. Proper selection of the of the output capacitor

and it’s ESR value determines stable operation and

optimizes performance. The typical application circuit

shown in Figure 1 was tested with a wide range of different

capacitors. The circuit was found to be unconditionally

stable with capacitor values from 10ìF to 2200ìF and ESR

ranging from 0.5mΩ to greater then 75mΩ.

5VCC

C1

0.1uF

VIN

C2

22uF

CNTL

4

EN

2

POK

1

VIN

3

VOUT

6

FB

7

8

GND

R3

10K

R2

12.5K

R1

10K

VOUT

C4

option

C3

100uF

Figure 1. Typical Application Circuit

Input capacitor: A minimum of 10uF ceramic capacitor is

recommended to be placed directly next to the VIN pin.

This allows for the device being some distance from any

bulk capacitance on the rail. Additionally, bulk capacitance

may be added closely to the input supply pin of the uP7706

to ensure that VIN does not sag, improving load transient

response.

Output capacitor: A minimum bulk capacitance of 33uF,

along with a 0.1uF ceramic decoupling capacitor is

recommended. Increasing the bulk capacitance will improve

the overall transient response. The use of multiple lower

value ceramic capacitors in parallel to achieve the desired

bulk capacitance will not cause stability issues. Although

designed for use with ceramic output capacitors, the uP7706

is extremely tolerant of output capacitor ESR values and

thus will also work comfortably with tantalum output

capacitors.

Thermal Consideration

The uP7706 integrates internal thermal limiting function to

protect the device from damage during fault conditions.

However, continuously keeping the junction near the thermal

shutdown temperature may remain possibility to affect

device reliability. It is highly recommended to keep the

junction temperature below the recommended operation

condition 125OC for maximum reliability.

Power dissipation in the device is calculated as:

PD = (VIN - VOUT) x IOUT + VCNTL x ICNTL

It is adequate to neglect power loss with respective to

control circuit VCNTL x ICNTL when considering thermal

management in uP7706 Take the following moderate

operation condition as an example: VIN = 2.5V, VOUT = 1.5V,

IOUT = 2A, the power dissipation is:

PD = (1.8V- 1.2V) x 2A = 2.0W

This power dissipation is conducted through the package

into the ambient environment, and, in the process, the

temperature of the die (TJ) rises above ambient. Large power

dissipation may cause considerable temperature raise in

the regulator in large dropout applications. The geometry

of the package and of the printed circuit board (PCB) greatly

influence how quickly the heat is transferred to the PCB

and away from the chip. The most commonly used thermal

metrics for IC packages are thermal resistance from the

chip junction to the ambient air surrounding the package

(θJA):

θJA = ( TJ -TA ) / PD

θJA specified in the Thermal Information section is measured

in the natural convection at TA = 25OC on a high effective

thermal conductivity test board (4 Layers, 2S2P) of JEDEC

51-7 thermal measurement standard. The case point of

uPI Semiconductor Corp., http://www.upi-semi.com

9

Rev. F00, File Name: uP7706-DS-F0000

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