TCM853 Просмотр технического описания (PDF) - TelCom Semiconductor Inc => Microchip

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TCM853

REGULATED GaAs FET BIAS SUPPLY

TelCom Semiconductor Inc => Microchip 

TCM850

TCM851

TCM852

TCM853

REGULATED GaAs FET BIAS SUPPLY

DETAILED DEVICE DESCRIPTION

The voltage applied to VIN is inverted by a capacitive

charge pump (using commutating capacitor C1 and reser-

voir capacitor C2). The negative voltage at NEGOUT is then

regulated by an internal linear regulator, the output of which

is connected to the OUT pin (Figure 1). The most negative

output voltage possible is the inverted input voltage (i.e.

–VIN) plus 1.0V (required by the post regulator). The linear

regulator reduces combined output noise (charge pump

ripple plus incoming supply noise) to 2mVp-p for the TCM850/

1/2 and 1mVp-p for the TCM853.

APPLICATIONS INFORMATION

Setting the Output Voltage

The TCM850/1/2 operate in the fixed output voltage

mode (OUT = – 4.1V) when the FB input is grounded (Figure

3). The output voltage can be adjusted by connecting FB to

the midpoint of a resistive voltage divider from OUT to GND

(Figure 4). Care must be taken to allow a minimum of 1.0V

across the linear regulator for proper regulation. The output

voltage is calculated using the formula below (R2 should be

chosen to be between 100kΩ and 400kΩ):

( ) VOUT = (–1.28) 1+RR21

C3

C1

C2

VIN

C+1

OUT

C–1

TCM850

TCM851

TCM852

NEGOUT

SHDN

SHDN

FB

OSC

GND

IOUT

VOUT = –2.56V

C4

10µF

R2 = 100k

R1 = 100k

All caps = 1.0µF unless otherwise noted

Figure 4. TCM850/851/852 Adjustable Application

The relationship between output voltage and control

voltage for the TCM853 (Figure 5) is given by:

( ) VOUT = VCTRL (–1.28)

R2

R1

C3

C1

C2

VIN

C+1

OUT

C–1

TCM850

TCM851

TCM852

NEGOUT

SHDN

SHDN

FB

OSC

GND

IOUT

VOUT = –4.1V

C4

10µF

All caps = 1.0µF unless otherwise noted

C3

C1

C2

VIN

C+1

OUT

C1–

TCM853

NEGOUT

IOUT

VOUT = – 0.5V to – 9.0V

C4

10µF

R2 = 100k

SHDN

CONT

GND

R1 = 100k

VCTRL (0 to 10V)

All caps = 1.0µF unless otherwise noted

4-30

Figure 3. TCM850/851/852 Standard Application

Figure 5. TCM853 Standard Application Circuit

TELCOM SEMICONDUCTOR, INC.

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