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# BQ25504 View Datasheet(PDF) - Texas Instruments

 Part Name Description Manufacturer BQ25504 Ultra Low-Power Boost Converter With Battery Management for Energy Harvester Applications Texas Instruments BQ25504 Datasheet PDF : 36 Pages
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bq25504
SLUSAH0C – OCTOBER 2011 – REVISED JUNE 2015
Typical Applications (continued)
• To size the VBAT_UV resistors, first choose RSUMUV = RUV1 + RUV2 = 10 Mthen solve Equation 2 for
RUV1
=
RSUMUV ´ VBIAS
VBATUV
=
10
MW ´1.25
2.2 V
V
=
5.68
MW
®
5.60
MW
closest
1%
value
then
(11)
• RUV2 = RSUMUV - RUV1 = 10 M- 5.60 M= 4.4 MΩ → 4.42 Mclosest 1% resistor resulting in
VBAT_UV = 2.2 V.
• With VBAT_OV VBAT_OK_HYST > VBAT_OK VBAT_UV, to size the VBAT_OK and VBAT_OK_HYST
resistors,
first choose RSUMOK = ROK1 + ROK2 + ROK3 = 10 Mthen solve Equation 4 and Equation 5 for
ROK1
=
VBIAS ´ RSUMOK
VBAT _ OK _ HYST
=
æ 1.25 V
èç 2.8 V
ö
ø÷
´
10
MW
=
4.46
MW
®
4.42
MW
closest
1%
resistor
then
(12)
ROK 2
=
æ
çè
VBAT _ OK _ PROG
VBIAS
-
ö
1÷ø
´
ROK1
=
æ 2.45
çè 1.25
V
V
-
ö
1÷ø
´
4.24
MW
=
4.07
MW,
then
(13)
• ROK3 = RSUMOK - ROK1 - ROK2 = 10 M- 4.42 M- 4.22 M= 1.36 MΩ → 1.43 Mto give
VBAT_OK = 2.44 V and VBAT_OK_HYST = 2.85 V.
• Keeping in mind that VREF_SAMP stores the MPP voltage for the harvester, first choose RSUMOC = ROC1 +
ROC2 = 20 Mthen solve Equation 1 for
ROC1
=
æ
ç
è
VREF _ SAMP
VIN _ DC(OC)
ö
÷
ø
´
RSUMOC
=
0.78 ´
20
MW
=
15.6
MW,
then
(14)
ROC2
=
RSUMOC
´ æçè1-
VREF _ SAMP
VIN _ DC(OC)
ö
÷ø
=
20
MW (1 -
0.78) =
4.4
MW
closest
1%
resistors
(15)
SLURAQ1 provides help on sizing and selecting the resistors.
9.2.1.3 Application Curves
VINDC = sourcemeter with VSOURCE = 1.0 V and compliance of
2.75 mA
VBAT connected to 0.1 F depleted supercap