MMPF0200Z datasheet(26/118 Pages) NXP

26 / 118 page

Analog Integrated Circuit Device Data



Freescale Semiconductor

PF0200Z

Functional Block Requirements and Behaviors

Bias and References Block Description

6.3.2

VREFDDR Voltage Reference

VREFDDR is an internal PMOS half supply voltage follower capable of supplying up to 10 mA. The output voltage is at one half

the input voltage. Its typically used as the reference voltage for DDR memories. A filtered resistor divider is utilized to create a

low-frequency pole. This divider then utilizes a voltage follower to drive the load.

Figure 7. VREFDDR Block Diagram

6.3.2.1

VREFDDR Control Register

The VREFDDR voltage reference is controlled by a single bit in VREFDDCRTL register in Table 18.

External Components

Table 18. Register VREFDDCRTL - ADDR 0x6A

Name

Bit #

R/W

Default

Description

UNUSED

3:0

–

0x00

UNUSED

VREFDDREN

R/W

0x00

Enable or disables VREFDDR output voltage

0 = VREFDDR Disabled

1 = VREFDDR Enabled

UNUSED

7:5

–

0x00

UNUSED

Table 19. VREFDDR External Components(27)

Capacitor

Capacitance (

F)

VINREFDDR(28) to VHALF

0.1

VHALF to GND

0.1

VREFDDR

1.0

Notes

27.

Use X5R or X7R capacitors.

28.

VINREFDDR to GND, 1.0

F minimum capacitance is provided by buck regulator output.

VINREFDDR

VREFDDR

VINREFDDR

CHALF1

Discharge

VHALF

VREFDDR

CHALF2

100 nf

CREFDDR

1.0 uf

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