Dual Tracking regulator circuit

A IC MAX634 inverting regulator is combined with a IC MAX630 to provide a dual tracking approximately 15 Volt output from a 12 Volt DC battery. The reference for the - 15 Volt output is derived from the positive output via R3 and R4. Both regulators are set to maximize output power at low battery voltages by reducing the oscillator frequency , via LBR, when V Batt falls to 8,5 volt.
Technical instruction :
Max. Input voltage    : 13 Volt / N/a mA
Max. Output voltage :-15 Volt , + 15 volt / 45 mA