keyboard/hhkb/doc/Power.txt

   1 HHKB Power consumption
   2 ----------------------
   3
   4 **Power consumption
   5     board   clock/prescaler     keyswitch   power ctrl      current
   6     --------------------------------------------------------------------------
   7     tmk     16MHz               no          no              26.4mA
   8     tmk     16MHz               pro1        no              45.1mA
   9     tmk     16MHz/2             no          no              18.1mA
  10     tmk     16MHz/2             pro1        no              37.3mA
  11     tmk     8MHz                no          no              18.9mA
  12     tmk     8MHz                pro2        no(w/o FET)     32.1mA
  13     tmk     8MHz                pro2        no(w FET)       32.1mA withou POWER_ON/FF
  14     tmk     8MHz                pro2        no(w FET)       32.6mA with POWR_ON/OFF
  15     tmk     8MHz                pro2        15ms(w FET)     21.3mA with POWR_ON/OFF, enumerated but error -32
  16     tmk     8MHz                pro2        60ms(w FET)     13.3mA with POWR_ON/OFF, not enumerated
  17
  18     gh60    16MHz                                           25.8mA
  19     gh60    16MHz               USB suspend w LED breathing 17.6-29.1mA
  20     gh60    16MHz               USB suspend w/o LED         0.2mA(0.231-0.276mA)
  21     Poker                                                    5.6mA
  22     Poker                       USB suspend                  0.3mA(0.301mA)
  23     gh60    16MHz               stock firmware by komar     26.8mA
  24
  25
  26     HHKB pro2 Over All                                     139.4mA
  27     HHKB pro2 Controller                                   115.1mA
  28     HHKB pro1 Controller                                    25.9mA
  29
  30
  31 keyswitch power consumption:
  32 pro1: 45.1-26.4=18.7mA
  33       37.3-18.1=19.2mA
  34 pro2: 32.1-18.9=13.2mA
  35
  36
  37
  38
  39
  40 **Low Freq Crystal or Prescaler?
  41 No advantage of Low Freq Crystal against Prescaled.
  42
  43 Clock routing
  44 X'tal --+---->Prescaler-------> System Clock
  45         |
  46         +---------------------> USB PLL
  47
  48 Design Decision: Install 16MHz crystal on board with using clock rescaler.