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Max 1797
on SurfBoard SIP Adapter
with a Potentiometer Dimmer Circuit

This design eliminates the need to etch a circuit board for the small surface mount chip.  Peripheral components are large "through hole" items soldered together on a blank board.

Results for Max 1674 are similar.


i, amps
(two white leds in parallel)
dV, volts, across 
R=.333 ohms
dV led, volts
0 0 2.40
.010 .0033 3.09
.020 .0066 3.25
.050 .0167 3.55
     
i, amps
(1 watt  Luxeon Star)
dV across 
R=.333 ohms
Vled
0 0 2.40
.100 .033 2.87
.200 .066 2.99
.275 .092 3.08
.300 .100 3.10
.325 .108 3.12
.350 .117 3.14

note:  R is three 1 ohm resistors in parallel.
1/R = (1/1) + (1/1) + (1/1) = 3, so R = .333 ohms



 
Output Voltage IC Operating Temperature, 
  Degrees C Degrees F
2.58 38 100
2.94 46 114
3.11 54 129

From Max1797 and Max 1674 data sheet:
Ambient temperature range is -40 C to 85 C, with a maximum junction temperature of 150 C


Efficiency:

dVin = .185 volts = I R
I = dV/R = .185/.333 = .555 amps
V bat (2C nimh) under load = 2.34 volts after going through R = .333 ohms
Vout to led under load = 3.15 volts, I led = .365 amps (extrapolated from data above)
P = V I
Pout/Pin = (3.15)(.365)/(2.34)(.555) = .885