Enabler II-G Assiste GPS Integration Guide - Farnell

Enfora Enabler III-G
Modem Integration Guide
White-LEDs Drivers 8-bit DAC Input Code, Output Current
The DC-DC step-up is based on a control loop, which is composed of a start-up circuit and an amplifier in
series with a comparator.
Another dedicated logic is capable to sense if one of the two white-LEDs series does not work properly
(open circuit): this logic prevents the divergence of the circuit, forcing a low-voltage level on the gate of
the power NMOS transistor in this case. During the normal operation, the NMOS transistors drivers,
which are part of the feedback system of the boost, remain saturated with a nominal drain-to-source
voltage closed to 1.2 V.
VBAT POUT 2 LEDs (mW) P OUT 3 LEDs (mW) P OUT 4 LEDs (mW)
5.5 586 873 824
5.4 586 831 834
5.2 586 812 767
5.0 586 799 710
4.8 586 755 645
4.6 586 683 572
4.4 586 637 523
4.2 586 606 487
4.0 586 583 457
3.8 586 535 424
3.6 586 468 377
3.4 586 425 330
3.3 586 401 304
VBAT (V)
2 LEDs
Max current (mA)
3 LEDs 4 LEDs
3.6 64 40 25.5
6.6.7. LED VRW (Pin 10)
The VRWLED voltage regulator is a step-up DC-DC converter supplying the White LEDs (20.0V/60mA).
The regulated voltage depends on the number of series White-LEDs. The main battery directly supplies
VRWLED.
VRWLED Parameter/Conditions Min Typ Max Units
Voltage out 20 Vdc
Current 60 mA
L = 2.2 μH ± 20%, RDC max = 100 mΩ, C = 2.2 µF ± 20% , Zener 20 V Iz typ = 5 mA (min: 4 mA, max: 10 mA), Pd typ = 0.3 W
(min: 0.25 W, max: 0.5 W);
GSM0308PB001 45 Version 1.03– 7/17/2007