AS3715 datasheet(34/160 Pages) AMSCO

34 / 160 page

Page 34

ams Datasheet, Confidential

Document Feedback

[v1-00] 2014-Sep-10

AS3715 − Detailed Description – Power Management Functions

Feedback Selection

For the step up the following feedback selections are possible

(selected by setpup2_fb): (see Figure 34)

Current Feedback

CURR1, CURR2 and CURR3 can be selected by setpup2_fb as a

current feedback pin.

The step-up converter is regulated such that the required

current at the feedback path can be supported. In this mode

the output voltage will be limited by limiting the voltage on the

selected feedback pin to 1.25V (select the external resistor

network and stepup2_v to adjust this limitation voltage).

stepup2_prot_dis has to be set to 0, otherwise the protection is

disabled.

Always choose the path with the higher voltage drop as

feedback to guarantee adequate supply for the other,

unregulated path.

Current Feedback with Automatic Feedback Selection

Same as above, but when currX_ctrl = 10b for the used current

sinks, the chip automatically selects the highest string (CURR1,

CURR2 or CURR3) as feedback input.

Voltage Feedback

The step-up converter output voltage is regulated by regulating

the selected feedback pin voltage to 1.25V.

Calculating Resistors for Voltage Feedback or

Over-Voltage Protection

Bit stepup_res should be set to 1 in voltage feedback mode

using two resistors.

The output voltage is regulated to a constant value, given by:

If R2 is not used, the output voltage is:

VSU: Step up regulator output voltage

R1 Feedback resistor R1

R2 Feedback resistor R2

IFB: Tuning current on FB_SU pin: stepup2_v

(0..31μA (1μA steps))

(EQ1)

VSU

R1 R2

------------------- 1.25 I



(EQ2)

VSU

1.25 IFB R1



AS3715 датащи(PDF) 34 Page - ams AG

AS3715 датащи(HTML) 34 Page - ams AG

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL