Beginning Microcontrollers with the MSP430

Thanks for the tip Steve !

-- Kris

>Anyway, I did some more digging and found the
MSP430 does have two
>different LCD driver options, the LCD and LCD_A, the LCD_A is in the
>newer models (42x0 and 461x) and does have an internal charge pump (I
>guess a lot people were asking for it and TI finally decided to put
>one in) and requires no external resistors, here is a good write up
>on both models
>
>http://www.eeplace.com/dm/3957/tw/5-1.pdf
>
>the LCD_A requires more power (due to the internal resister ladder)
>but less parts and has contrast control, and as you say results in a
>bigger die. But I think the total board area will be reduced

--- In msp430@msp4..., Matt Pobursky <ccsuser@...> wrote:
>
> Nope. The LCD drivers are simply analog switches that supply the LCD
> mux voltages from the external voltages on the R33, R23, R13 and R03
> pins. 
> 
> When I started using the MSP4304xx series a few years ago I asked 
the
> TI factory engineers why they didn't
implement a charge pump for the
> LCD. Their answer was that it added quite a bit of die space and 
power
> consumption for something that maybe 50% of users
need. It makes 
sense
> -- since then I've done about a dozen LCD
designs and haven't 
needed to
> step up the battery voltage to drive an LCD. 
> 
> You could specify a low voltage LCD (~1.8V) or use a battery that 
never
> drops below your minimum LCD "on"
voltage.
> 

Yes, but I'm trying to eliminate a second battery as nothing else is 
the system requires anything above 2 volts. Do they make LCD's that 
work at 1.8V? All I see is 3.3V and 5 Volt, even custom models.

Anyway, I did some more digging and found the MSP430 does have two 
different LCD driver options, the LCD and LCD_A, the LCD_A is in the 
newer models (42x0 and 461x) and does have an internal charge pump (I 
guess a lot people were asking for it and TI finally decided to put 
one in) and requires no external resistors, here is a good write up 
on both models

http://www.eeplace.com/dm/3957/tw/5-1.pdf

the LCD_A requires more power (due to the internal resister ladder) 
but less parts and has contrast control, and as you say results in a 
bigger die. But I think the total board area will be reduced

Steve,

The LCD biasing voltages are set in voltage divider, where the top voltage
simply is Vdd.
There is no charge pump AFAIK, so for 3.3 V LCD you must supply 3.3 V for Vdd.

-- Kris

>-----Original Message-----
>From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of
>bungalow_steve
>Sent: Thursday, 1 June 2006 4:38 AM
>To: msp430@msp4...
>Subject: [msp430] MSP430 LCD driver voltage range
>
>Do the MSP430 with LCD drivers drive 3.3 LCD's down to the low 1.8V
>supply range? At first I just assumed they have charge pumps/voltage
>multipliers/step up converters  to supply the 3.3 Volts to the LCDs
>like other micro's, but didn't see anything in the data sheet to
>suggest such
>thanks
>
>
>
>
>
>
>
>
>.
>
>
>Yahoo! Groups Links
>
>
>
>
>
>

Nope. The LCD drivers are simply analog switches that supply the LCD
mux voltages from the external voltages on the R33, R23, R13 and R03
pins. 

When I started using the MSP4304xx series a few years ago I asked the
TI factory engineers why they didn't implement a charge pump for the
LCD. Their answer was that it added quite a bit of die space and power
consumption for something that maybe 50% of users need. It makes sense
-- since then I've done about a dozen LCD designs and haven't needed
to
step up the battery voltage to drive an LCD. 

You could specify a low voltage LCD (~1.8V) or use a battery that never
drops below your minimum LCD "on" voltage.

Matt Pobursky
Maximum Performance Systems

On Wed, 31 May 2006 18:37:38 -0000, bungalow_steve
wrote:
> Do the MSP430 with LCD drivers drive 3.3 LCD's down to the low 1.8V
> supply range? At first I just assumed they have charge pumps/voltage
> multipliers/step up converters  to supply the 3.3 Volts to the LCDs
> like other micro's, but didn't see anything in the data sheet to
> suggest such
> thanks

Do the MSP430 with LCD drivers drive 3.3 LCD's down to the low 1.8V 
supply range? At first I just assumed they have charge pumps/voltage 
multipliers/step up converters  to supply the 3.3 Volts to the LCDs 
like other micro's, but didn't see anything in the data sheet to 
suggest such
thanks