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BQ25504 View Datasheet(PDF) - Texas Instruments

Part NameDescriptionManufacturer
BQ25504 Ultra Low-Power Boost Converter With Battery Management for Energy Harvester Applications Texas-Instruments
Texas Instruments Texas-Instruments
BQ25504 Datasheet PDF : 36 Pages
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bq25504
SLUSAH0C – OCTOBER 2011 – REVISED JUNE 2015
9.2 Typical Applications
9.2.1 Solar Application Circuit
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Solar +
Cell
-
LBST CBYP (1)
22µH
CSTOR(2)
4.7 µF
(min)
Battery(>100µF)
CHVR
4.7µF
VSTOR
16 15 ` 14
LBST VSTOR
1 VSS
VBAT
13
VSS
AVSS 12
ROC2
4.42 MΩ
ROC 1
15.62MΩ
2 VIN_DC
VBAT_OK 11
bq25504
3 VOC_SAMP
OK_PROG 10
CREF
4 VREF_SAMP
OK_HYST 9
0.01µF
OT_PROG VBAT_OV VRDIV VBAT _UV
5
6
7
8
ROK1
4.42 MΩ
ROK2
4.22 MΩ
ROK3
1. 43 MΩ
VBAT_OK
ROV2
4.02MΩ
ROV1
5.90MΩ
RUV2
4.42 MΩ
RUV 1
5.60 MΩ
(1) Place close as possible to IC pin 15 (VSTOR) and pin 13 (VSS)
(2) See the Capacitor Selection section for guidance on sizing CSTOR
Figure 14. Typical Solar Application Circuit
9.2.1.1 Design Requirements
The desired voltage levels are VBAT_OV = 3.15 V, VBAT_UV = 2.20 V, VBAT_OK = 2.44 V, VBAT_OK_HYST =
2.80 V and MPP (VOC) = 78% which is typical for solar panels. There are no large load transients expected. The
IC must stop charging if its junction temperature is above 65°C. The simulated solar panel open circuit voltage is
1.0 V.
9.2.1.2 Detailed Design Procedure
The recommended L1 = 22 µH, CBYP = 0.01 µF and low leakage CREF = 10 nF are selected. In order to ensure
the fastest recovery of the harvester output voltage to the MPPT level following power extraction, the minimum
recommended CIN = 4.7 µF is selected. Because no large system load transients are expected and to ensure
fast charge time during cold start, the minimum recommended CSTOR = 4.7 µF. To stop charging when the IC
junction temperature is above 65°C, the OT_PROG pin is tied to ground.
• With VBAT_UV < VBAT_OV 5.5 V, to size the VBAT_OV resistors, first choose RSUMOV = ROV1 + ROV2 =
10 Mthen solve Equation 3 for
ROV1
=
3
2
´
RSUMOV ´ VBIAS
VBAT _ OV
´
3
2
10
MW ´1.25
3.15 V
V
=
5.95
MW
®
5.90
MW
closest
1%
value
then
(10)
• ROV2 = RSUMOV - ROV1 = 10 M- 5.95 M= 4.05 MΩ → 4.02 Mresulting in VBAT_OV = 3.15 V
18
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