DC-DC converter (boost) can't charge cellphone

[[email protected]]

Hello everyone,

I'm new to electronics design, when building DC-DC converter to charge
cellphone, I noticed it did not work. I tried MAX1797, I can get the
output voltage: +5.1V, which is good for Moto RAZR, but for some
reason, I suspect the output current is not good enough. From the spec,
it appears the converter can generate typical Iout = 0.55A.

The link to this IC:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2377

I did not add any other circuit, just used the circuit from Evaluation
kit and adjust R1 and R2 to get Vo=+5.1V.

http://www.maxim-ic.com/quick_view2.cfm?qv_pk=2512

I can measure the current to the cellphone, it's around 5mA instead of
around several hundreds of mA (i.e. 500mA), the although the voltage is
+5.1 as expected.

I connect the output Vout to cellphone's charging Pin (Vbus of MiniUSB)
and also connected GND to cellphone GND. I can hear cellphone is
detecting a charger (a beep sound), but it did not charge, if I remove
my circuit, got beep again which means "charger" removing detected.

Anyone has idea why it did not work?

Thanks,
Gary

 

[mpm]

Anyone has idea why it did not work?

Gary,
Charing batteries is getting to be more of an art than science these
days.
I don't know if this is the case with the Razor, but I've seen chargers
that want to "communicate" with the battery pack before re-charging.
It's not simply a matter of providing voltage anymore.

I think in part, this has to do with so many different battery designs
out there. Many, having the same form factor. By communicating with
the battery first, the charger can "know" what type of battery chemisty
is being used in the device, or for that matter, whether the battery is
even a re-chargeable type.

I also think this is a way for manufacturers to force people to by
their (and only their) chargers.!?
Of course, that could just be the cynic in me...

You can always verify your charger design with a power resistor.
If you get the expected rated voltage and current, it's probably OK.
-mpm

 

[Jim Thompson]

Gary,
Charing batteries is getting to be more of an art than science these
days.
I don't know if this is the case with the Razor, but I've seen chargers
that want to "communicate" with the battery pack before re-charging.
It's not simply a matter of providing voltage anymore.

Yep. LiIon and NiMH batteries are "smart" and require matching
chargers.

I think in part, this has to do with so many different battery designs
out there. Many, having the same form factor. By communicating with
the battery first, the charger can "know" what type of battery chemisty
is being used in the device, or for that matter, whether the battery is
even a re-chargeable type.

I also think this is a way for manufacturers to force people to by
their (and only their) chargers.!?
Of course, that could just be the cynic in me...

You can always verify your charger design with a power resistor.
If you get the expected rated voltage and current, it's probably OK.
-mpm

...Jim Thompson

 

[[email protected]]

Hello everyone,

I'm new to electronics design, when building DC-DC converter to charge
cellphone, I noticed it did not work. I tried MAX1797, I can get the
output voltage: +5.1V, which is good for Moto RAZR, but for some
reason, I suspect the output current is not good enough. From the spec,
it appears the converter can generate typical Iout = 0.55A.

The link to this IC:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2377

I did not add any other circuit, just used the circuit from Evaluation
kit and adjust R1 and R2 to get Vo=+5.1V.

http://www.maxim-ic.com/quick_view2.cfm?qv_pk=2512

I can measure the current to the cellphone, it's around 5mA instead of
around several hundreds of mA (i.e. 500mA), the although the voltage is
+5.1 as expected.

I connect the output Vout to cellphone's charging Pin (Vbus of MiniUSB)
and also connected GND to cellphone GND. I can hear cellphone is
detecting a charger (a beep sound), but it did not charge, if I remove
my circuit, got beep again which means "charger" removing detected.

Anyone has idea why it did not work?

Thanks,
Gary

go to walmart and buy the $9.74 motorola v3 mobile power cord
http://www.walmart.com/catalog/product.do?product_id=4122603

 

[[email protected]]

Thanks all.
Gary

 

[Paul Hovnanian P.E.]

Hello everyone,

I'm new to electronics design, when building DC-DC converter to charge
cellphone, I noticed it did not work. I tried MAX1797, I can get the
output voltage: +5.1V, which is good for Moto RAZR, but for some
reason, I suspect the output current is not good enough. From the spec,
it appears the converter can generate typical Iout = 0.55A.

The Razr charges through a USB port. Because of this, it needs to
negotiate with the supply to determine the available capacity. If it
cannot do so (per the USB interface spec) it may refuse to draw
sufficient power to charge its batteries. This is what I suspect is
going on.