Rainbow-electronics MAX686 Bedienungsanleitung PDF herunterladen (Seite 7)

MAX686

DAC-Controlled Boost/Inverter

LCD Bias Supply with Internal Switch

_______________________________________________________________________________________ 7

_____________________________Typical Operating Characteristics (continued)

(Circuits of Figures 1 and 2, V

= V

= +5V, L1 = 22µH, SHDN = V

, C

REF

= 0.1µF, T

= +25°C, unless otherwise noted.)

OUT

5V/div

-16.8V

POWER-UP RESPONSE

(NEGATIVE CONFIGURATION)

MAX686 TOC14A

500µs

SHDN

5V/div

SET

= V

= 4.7kΩ

OUT

5V/div

-16.8V

POWER-DOWN RESPONSE

(NEGATIVE CONFIGURATION)

MAX686 TOC14B

20ms/div

SHDN

5V/div

SET

= V

= 4.7kΩ

Reference Output. Bypass with a 0.1µF ceramic capacitor to GND.REF9

Feedback Input. Connect to an external voltage divider to set the MAX686 output voltage. See the section

Setting the Output Voltage with the DAC

FB10

Power-OK Sense Input/Power-OK Comparator Input. When the voltage applied to POK is greater than

1.125V, LCDON is low. Connect to a resistive voltage divider monitoring V

or V

OUT

POK11

IC Power-Supply InputV

GroundGND13

Gate-Drive Supply for Internal MOSFET. Connect to V

Set LX Current Limit. Sets the peak current limit for the internal switch. Connect to V

for 500mA current

limit. Connect to GND for 250mA current limit.

ISET6

Shutdown Input. A logic low on SHDN places the MAX686 in shutdown mode. Connect to V

for normal

operation.

SHDN

DAC Output VoltageDACOUT8

Polarity Input. Changes polarity and threshold of FB to allow regulation of either positive or negative output

voltages. POL also changes the polarity of the DAC output such that increasing codes always increases the

magnitude of the output voltage. Set POL = GND for positive output voltage, or set POL = V

for negative

output voltage.

POL4

Decrement Output Voltage Input. Decrements the DAC on each rising edge such that

OUT

decreases.

DN3

Increment Output Voltage Input. Increments the DAC on each rising edge such that

OUT

increases.

UP2

Power Ground. Connect to GND.PGND1

FUNCTIONNAME

Power-OK Comparator Open-Drain Output. Connect to external switch to turn LCD power on or off. See the

section

Controlling the LCD Using POK and LCDON

LCDON

No Connection. Not internally connected.N.C.15

Drain of Internal 28V, 500mA N-Channel SwitchLX16

Pin Description

1 2 3 4 5 6 7 8 9 10 11 12 ... 15 16

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