ETC BQ25504

Texas Instruments Asia
新聞稿
TIA-11110
德州儀器推出高效率升壓充電 IC
支援奈米電力能源採集應用
330 nA 靜態電流與 330 mV 冷開機功能
有助降低無線感測器網路成本
(台北訊，2011 年 11 月 07 日) 德州儀器 (TI) 宣佈推出適用於能源採集的新一代電源管
理 IC。支援奈米 (超低) 電源採集的高效率升壓充電器，可管理各種能源產生的微瓦
(microwatts) 至毫瓦 (milliwatts) 等級電源，包含太陽能、電熱、電磁與振動等，並可將
採集到的能源儲蓄在各種儲存裝置中，包括鋰電池與超級電容器 (super capacitor)。該
bq25504 具有保護能源儲存裝置的電路，免於過壓或欠壓影響，在電池深度放電時啟動
系統。 bq25504 詳細產品資訊或訂購樣品，請參見網頁：http://www.ti.com/bq25504prtw。
舉例來說，以太陽能面板為提供室內光照條件的手持設備供電，此款最新升壓充電器
與線性穩壓器相比，可將收集的可用能源提升 30% 至 70%。效率提升有助於設計人員
減少設計方案中太陽能面板數量，縮減尺寸，降低整體解決方案成本。該元件可為無
線感測器網路 (WSN) 帶來極大優勢，支援區域、工業、水/廢棄物及結構監控，也可滿
足消費應用、高可靠度以及醫療應用的需求。
TI 電源管理事業群資深副總裁 Sami Kiriaki 指出，無線感測器網路由於感測器節點的
電池維護與替換成本，一直難以廣泛推廣。隨著 bq25504 升壓充電器的推出，節點現
在可自動供電，降低營運成本，將超低功耗無線感測器網路實現於更多應用中，滿足
危險或管制區域的工業監控等需求。
主要特性與優勢
 330 nA (標準值) 低暫態電流，超過 80% 的高轉換效率，大幅提升能源採集器收集
的能量；
 最大功率點追蹤 (MPPT) 技術，可針對不同光照條件下的太陽能面板與不同溫度條
件下的熱發電機 (TEG)，優化 DC 採集器收集能源功能；
 使用者可編程設計設定，使升壓充電器 IC 可用於各種能源及儲存裝置，包括不同
化學成分的電池或超級電容器等；
1


330 mV (標準值) 低冷開機電壓讓 bq25504 可透過低電壓電源啟動，如低光照下的
單一太陽能面板或低溫差 TEG 等；
良好電池狀態指示器，可條件式啟動外部負載，保護存放裝置。
工具與支援
TI 提供種類繁多的工具與支援加速超低功耗能源採集的實作，其中包含：
 bq25504 評估模組：www.ti.com/bq25504evm-pr；
 bq25504 EVM 使用者指南：www.ti.com/bq25504evmuser-pr。
供貨與價格
採用 3 mm x 3 mm VQFN 封裝的 bq25504 升壓轉換器，現已開始供貨，每千顆單位建
議售價為 2.10 美元。
TI 能源採集與無線連接產品系列：
 參與 TI E2E™ 社群的電池論壇的互動討論：www.ti.com/batteryforum-pr；





下載 TI 新版電池管理解決方案指南：www.ti.com/battery-pr；
下載 TI 能源收集產品型錄：www.ti.com/energybrochure-pr；
下載 TI 無線連接解決方案指南：www.ti.com/wireconnguide-pr。
透過 Plurk 與 TI 即時互動：http://www.plurk.com/TITW
透過 Twitter 與 TI 即時互動：http://twitter.com/TXInstrumentsTW
TI 電池管理解決方案
TI 提供支援所有高效能產品的完整電池管理產品系列。涵蓋從電池充電器到高精度
Impedance Track™ 電量監測計的各種元件，包含電源保護與認證 IC，以及支援太陽能
與無線電源等充電電源元件。
# # #
關於德州儀器
德州儀器半導體創新產品協助 超過 80,000 個客戶發揮無限可能性，使科技更加智慧、
安全、環保、健康且充滿樂趣。TI 秉持開創更美好未來的承諾，並將其體現於所言所
行 – 從以負責任的態度生產製造半導體、照顧員工，以及回饋社會，而這只是 TI 實踐
承諾的序幕。更多詳細資訊，請參訪網頁 www.ti.com。
商標
TI E2E 與 Impedance Track 是德州儀器的商標。所有註冊商標與其它商標均歸其各自所
有者所有。
新聞聯絡人：
王綺
德州儀器
柏驊晟 / 譚毓芬
經典公關
2
電話：+86-21-2307-3662
[email protected]
電話：+886-2-7718-7777 分機 528 / 580
[email protected]
[email protected]
3
bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
Ultra Low Power Boost Converter with Battery Management for Energy Harvester
Applications
Check for Samples: bq25504
FEATURES
1
•
•
•
•
Ultra Low Power With High Efficiency DC/DC
Boost Converter/Charger
– Continuous Energy Harvesting From Low
Input Sources: VIN ≥ 80 mV(Typical)
– Ultra Low Quiescent Current: IQ < 330 nA
(Typical)
– Cold-Start Voltage: VIN ≥ 330 mV (Typical)
Programmable Dynamic Maximum Power Point
Tracking (MPPT)
– Integrated Dynamic Maximum Power Point
Tracking for Optimal Energy Extraction
From a Variety of Energy Generation
Sources
– Input Voltage Regulation Prevents
Collapsing Input Source
Energy Storage
– Energy can be Stored to Re-Chargeable
Li-ion Batteries, Thin-film Batteries,
Super-Capacitors, or Conventional
Capacitors
Battery Charging and Protection
– User Programmable Undervoltage /
Overvoltage Levels
– On-Chip Temperature Sensor with
Programmable Overtemperature Shutoff
•
Battery Status Output
– Battery Good Output Pin
– Programmable Threshold and Hysteresis
– Warn Attached Microcontrollers of Pending
Loss of Power
– Can be Used to Enable/Disable System
Loads
APPLICATIONS
•
•
•
•
•
•
•
•
•
•
Energy Harvesting
Solar Charger
Thermal Electric Generator (TEG) Harvesting
Wireless Sensor Networks (WSN)
Industrial Monitoring
Environmental Monitoring
Bridge / Structural Health Monitoring (SHM)
Smart Building Controls
Portable and Wearable Health Devices
Entertainment System Remote Controls
LBST
CSTOR
Battery
CHVR
Solar
Cell
SYSTEM
LOAD
VSTOR
+
-
16
15
LBST
VSTOR
1
VSS
2
VIN_DC
`
14
13
VBAT
VSS
AVSS
12
VBAT_OK
11
bq25504
ROC 2
ROC 1
VBAT_OK
3
VOC_SAMP
OK_PROG
10
4
VREF_SAMP
OK_HYST
9
CREF
ROK1
ROK2
OT_PROG VBAT_OV VRDIV VBAT _UV
5
6
7
ROK3
8
ROV2
RUV 2
ROV1
RUV 1
DESCRIPTION
The bq25504 is the first of a new family of intelligent integrated energy harvesting Nano-Power management
solutions that are well suited for meeting the special needs of ultra low power applications. The product is
specifically designed to efficiently acquire and manage the microwatts (µW) to miliwatts (mW) of power
generated from a variety of DC sources like photovoltaic (solar) or thermal electric generators. The bq25504 is
the first device of its kind to implement a highly efficient boost converter/charger targeted toward products and
systems, such as wireless sensor networks (WSN) which have stringent power and operational demands. The
design of the bq25504 starts with a DCDC boost converter/charger that requires only microwatts of power to
begin operating.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011, Texas Instruments Incorporated
bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
DESCRIPTION CONTINUED
Once started, the boost converter/charger can effectively extract power from low voltage output harvesters such
as thermoelectric generators (TEGs) or single or dual cell solar panels. The boost converter can be started with
VIN as low as 330 mV, and once started, can continue to harvest energy down to VIN = 80 mV.
The bq25504 also implements a programmable maximum power point tracking sampling network to optimize the
transfer of power into the device. Sampling the VIN_DC open circuit voltage is programmed using external
resistors, and held with an external capacitor (CREF).
For example solar cells that operate at maximum power point (MPP) of 80% of their open circuit voltage, the
resistor divider can be set to 80% of the VIN_DC voltage and the network will control the VIN_DC to operate
near that sampled reference voltage. Alternatively, an external reference voltage can be provide by a MCU to
produce a more complex MPPT algorithm.
The bq25504 was designed with the flexibility to support a variety of energy storage elements. The availability of
the sources from which harvesters extract their energy can often be sporadic or time-varying. Systems will
typically need some type of energy storage element, such as a re-chargeable battery, super capacitor, or
conventional capacitor. The storage element will make certain constant power is available when needed for the
systems. The storage element also allows the system to handle any peak currents that can not directly come
from the input source.
To prevent damage to a customer’s storage element, both maximum and minimum voltages are monitored
against the user programmed undervoltage (UV) and overvoltage (OV) levels.
To further assist users in the strict management of their energy budgets, the bq25504 toggles the battery good
flag to signal an attached microprocessor when the voltage on an energy storage battery or capacitor has
dropped below a pre-set critical level. This should trigger the shedding of load currents to prevent the system
from entering an undervoltage condition. The OV, UV and battery good thresholds are programmed
independently.
All the capabilities of bq25504 are packed into a small foot-print 16-lead 3 mm x 3 mm QFN package.
ORDERING INFORMATION
(1)
PART NO.
PACKAGE
bq25504
QFN 16 pin 3 mm x 3 mm
ORDERING NUMBER
(TAPE AND REEL) (1)
PACKAGE
MARKING
QUANTITY
BQ25504RGTR
B5504
3000
BQ25504RGTT
B5504
250
The RGW package is available in tape on reel. Add R suffix to order quantities of 3000 parts per reel, T suffix for 250 parts per reel.
ABSOLUTE MAXIMUM RATINGS (1)
over operating free-air temperature range (unless otherwise noted)
VALUE
UNIT
MIN
MAX
–0.3
5.5
V
400
mW
Operating junction temperature range, TJ
–40
125
°C
Storage temperature range, TSTG
–65
150
°C
Input voltage
Peak Input Power, PIN_PK
(1)
(2)
2
VIN_DC, VOC_SAMP, VREF_SAMP, VBAT_OV, VBAT_UV, VRDIV,
OK_HYST, OK_PROG, VBAT_OK, VBAT, VSTOR, LBST (2)
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating
conditions” is not implied. Exposure to absolute–maximum–rated conditions for extended periods may affect device reliability.
All voltage values are with respect to VSS/ground terminal.
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Copyright © 2011, Texas Instruments Incorporated
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bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
THERMAL INFORMATION
bq25504
THERMAL METRIC (1) (2)
θJA
Junction-to-ambient thermal resistance
48.5
θJCtop
Junction-to-case (top) thermal resistance
63.9
θJB
Junction-to-board thermal resistance
22
ψJT
Junction-to-top characterization parameter
1.8
ψJB
Junction-to-board characterization parameter
22
θJCbot
Junction-to-case (bottom) thermal resistance
6.5
(1)
(2)
UNITS
RGT (16 PINS)
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
For thermal estimates of this device based on PCB copper area, see the TI PCB Thermal Calculator.
RECOMMENDED OPERATING CONDITIONS
MIN
DC input voltage into VIN_DC (1)
VIN (DC)
NOM
0.13
(2)
MAX
UNIT
3
2.5
V
VBAT
Battery voltage range
5.25
V
CHVR
Input capacitance
4.23
4.7
5.17
µF
CSTOR
Storage capacitance
4.23
4.7
5.17
µF
CBAT
Battery pin capacitance or equivalent battery capacity
100
CREF
Sampled reference storage capacitance
9
10
11
nF
ROC1 + ROC2
Total resistance for setting for MPPT reference.
18
20
22
MΩ
µF
ROK1 + ROK2 + ROK3
Total resistance for setting reference voltage.
9
10
11
MΩ
RUV1 + RUV2
Total resistance for setting reference voltage.
9
10
11
MΩ
ROV1 + ROV2
Total resistance for setting reference voltage.
9
10
11
MΩ
LBST
Input inductance
19.8
22
24.2
µH
TA
Operating free air ambient temperature
–40
85
°C
TJ
Operating junction temperature
–40
105
°C
(1)
(2)
Maximum input power ≤ 300 mW. Cold start has been completed
VBAT_OV setting must be higher than VIN_DC
ELECTRICAL CHARACTERISTICS
Over recommended temperature range, typical values are at TA = 25°C. Unless otherwise noted, specifications apply for
conditions of VIN_DC = 1.2V, VBAT = VSTOR = 3V. External components LBST = 22 µH, CHVR = 4.7 µF CSTOR= 4.7 µF.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
3000
mV
BOOST CONVERTER \ CHARGER STAGE
VIN (DC)
DC input voltage into VIN_DC
Cold-start completed
IIN (DC)
Peak Current flowing from VIN into VIN_DC input
0.5V < VIN < 3 V; VSTOR = 4.2 V
PIN
Input power range for normal charging
VBAT > VIN_DC; VIN_DC = 0.5 V
VINCS
Cold-start Voltage. Input voltage that will start
charging of VSTOR
VBAT < VBAT_UV; VSTOR = 0 V;
0°C < TA < 85°C
PIN CS
Minimum cold-start input power to start normal
charging
VBAT < VBAT_UV; VSTOR = 0 V; Input source
impedance 0 Ω
VSTOR_CHGEN
Voltage on VSTOR when cold start operation ends
and normal charger operation begins
RBAT(on)
Resistance of switch between VBAT and VSTOR
when turned on.
130
200
300
mA
300
mW
330
450
mV
10
50
µW
1.77
1.95
V
VBAT = 4.2 V; VSTOR load = 50 mA
2
Ω
VBAT = 2.1 V
2
VBAT = 4.2 V
2
VBAT = 2.1 V
5
VBAT = 4.2 V
5
0.01
1.6
Charger Low Side switch ON resistance
RDS(on)
Charger rectifier High Side switch ON resistance
fSW_BST
Boost converter mode switching frequency
1
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Ω
Ω
MHz
3
bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Over recommended temperature range, typical values are at TA = 25°C. Unless otherwise noted, specifications apply for
conditions of VIN_DC = 1.2V, VBAT = VSTOR = 3V. External components LBST = 22 µH, CHVR = 4.7 µF CSTOR= 4.7 µF.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1
5
nA
80
nA
BATTERY MANAGEMENT
VBAT = 2.1 V; VBAT_UV = 2.3 V, TJ = 25°C
VSTOR = 0 V
I(VBAT)
Leakage on VBAT pin
VBAT = 2.1 V; VBAT_UV = 2.3 V,
–40°C < TJ < 65°C, VSTOR = 0 V
VSTOR Quiescent current Charger Shutdown in UV
Condition
VIN_DC = 0V;
VBAT < VBAT_UV = 2.4V;
VSTOR = 2.2V, No load on VBAT
330
750
nA
VSTOR Quiescent current Charger Shutdown in OV
Condition
VIN_DC = 0V,
VBAT > VBAT_OV, VSTOR = 4.25,
No load on VBAT
570
1400
nA
VBAT_OV
Programmable voltage range for overvoltage
threshold (Battery voltage is rising)
VBAT increasing
2.5
5.25
V
VBAT_OV_HYST
Battery voltage overvoltage hysteresis threshold
(Battery voltage is falling), internal threshold
VBAT decreasing
18
VBAT_UV
Programmable voltage range for under voltage
threshold (Battery voltage is falling)
VBAT decreasing; VBAT_UV > VBias
2.2
VBAT_UV_HYST
Battery under voltage threshold hysteresis, internal
thershold
VBAT increasing
40
VBAT_OK
Programmable voltage range for threshold voltage
for high to low transition of digital signal indicating
battery is OK,
VBAT decreasing
VBAT_OK_HYST
Programmable voltage range for threshold voltage
for low to high transition of digital signal indicating
battery is OK,
VBAT increasing
VBAT_ACCURACY
Overall Accuracy for threshold values, UV, OV,
VBAT_OK
Selected resistors are 0.1% tolerance
VBAT_OKH
VBAT OK (High) threshold voltage
Load = 10 µA
VBAT_OKL
VBAT OK (Low) threshold voltage
Load = 10 µA
TSD_PROTL
The temperature at which the boost converter is
disabled and the switch between VBAT and VSTOR
is disconnected to protect the battery
OT_Prog = LO
65
OT_Prog = HI
120
I(VSTOR)
TSD_PROTH
Voltage for OT_PROG High setting
35
89
VBAT_OV
80
125
mV
V
mV
VBAT_UV
VBAT_OV
V
50
VBAT_OVVBAT_UV
mV
–5%
5%
VSTOR200mV
100
V
mV
°C
2
V
OT_Prog
Voltage for OT_PROG Low setting
0.3
V
BIAS and MPPT CONTROL STAGE
VOC_sample
Sampling period of VIN_DC open circuit voltage
16
s
VOC_Settling
Sampling period of VIN_DC open circuit voltage
256
ms
VIN_Reg
Regulation of VIN_DC during charging
VIN_shutoff
DC input voltage into VIN_DC when charger is
turned off
MPPT_Disable
Threshold on VOC_SAMP to disable MPPT
functionality
VBIAS
Voltage node which is used as reference for the
programmable voltage thresholds
4
0.5 V <VIN < 3 V; IIN (DC) = 10 mA
–10%
40
10%
80
130
VSTOR-15
mV
VIN_DC ≥ 0.5V; VSTOR ≥ 1.8 V
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1.21
mV
V
1.25
1.27
V
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s) :bq25504
bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
DEVICE INFORMATION
RGT PACKAGE
(TOP VIEW)
16
15
LBST
VSTOR
`
14
13
VBAT
VSS
1
VSS
2
VIN_DC
3
VOC_SAMP
OK_PROG
10
VREF_SAMP
OK_HYST
9
AVSS
12
VBAT_OK
11
bq25504
4
OT_PROG VBAT_OV VRDIV VBAT_UV
5
6
7
8
Figure 1. bq25504 3mm x 3mm QFN-16 Package
PIN FUNCTIONS
PIN
NO.
NAME
I/O TYPE
DESCRIPTION
1
VSS
Input
2
VIN_DC
Input
DC voltage input from energy harvesters
3
VOC_SAMP
Input
Sampling pin for MPPT network. To disable MPPT, connect to VSTOR
4
VREF_SAMP
Input
Switched node for holding the reference set by resistors on VOC_SAMP for MPPT. When MPPT is
disabled, input for reference voltage
5
OT_PROG
Input
Digital Programming input for overtemperature threshold
6
VBAT_OV
Input
Resistor divider input for over voltage threshold
7
VRDIV
8
VBAT_UV
Input
Resistor divider input for under voltage threshold
9
OK_HYST
Input
Resistor divider input for VBAT_OK hysteresis threshold
10
OK_PROG
Input
Resistor divider input for VBAT_OK threshold
11
VBAT_OK
Output
Digital battery good indicator referenced to VSTOR pin
12
AVSS
Supply
Signal ground connection for the device
13
VSS
Supply
General ground connection for the device
14
VBAT
15
VSTOR
16
LBST
Output
I/O
Output
Input
General ground connection for the device
Resistor divider biasing voltage.
Connection for storage elements
Connection for the system load, output of the boost converter
Inductor connection for the boost converter switching node
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5
bq25504
SLUSAH0 – OCTOBER 2011
www.ti.com
TYPICAL APPLICATION CIRCUITS
VIN_DC = 1.2 V, CSTOR= 4.7 µF, LBST= 22 µH, CHVR= 4.7 µF, CREF= 10 nF, TSD_PROTL (65°C),
MPPT (VOC) = 80% VBAT_OV = 3.1 V, VBAT_UV = 2.2 V, VBAT_OK = 2.4 V, VBAT_OK_HYST = 2.8 V,
ROK1 = 4.42 MΩ, ROK2 = 4.22 MΩ, ROK3 = 1.43 MΩ, ROV1 = 5.9 MΩ, ROV2 = 4.02 MΩ,
RUV1= 5.6 MΩ, RUV2 = 4.42 MΩ, ROC1= 15.62 MΩ, ROC2 = 4.42 MΩ
LBST
CSTOR
4.7µF
Battery(>100µF)
22µH
Solar
Cell
+
VSTOR
CHVR
4.7µF
1
-
16
15
LBST
VSTOR
`
14
13
VBAT
VSS
VSS
AVSS
12
VBAT_OK
2
ROC2
VIN_DC
11
ROK1
bq25504
4.42 MΩ
ROC 1
15.62MΩ
VBAT_OK
3
VOC_SAMP
4
VREF_SAMP
OK_PROG
CREF
0.01µF
OK_HYST
10
9
6
7
ROV2
4.02MΩ
ROV1
5.90MΩ
ROK2
4.22 MΩ
ROK3
OT_PROG VBAT_OV VRDIV VBAT _UV
5
4.42 MΩ
8
1.43MΩ
RUV2
4.42 MΩ
RUV 1
5.60 MΩ
Figure 2. Typical Solar Application Circuit
6
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VIN_DC = 0.5 V, CSTOR = 4.7 µF, LBST = 22 µH, CHVR = 4.7 µF, CREF = 10 nF, TSD_PROTH (120°C),
MPPT (VOC) = 50% VBAT_OV = 4.2 V, VBAT_UV = 3.2 V, VBAT_OK = 3.5 V, VBAT_OK_HYST = 3.7 V,
ROK1 = 3.32 MΩ, ROK2 = 6.12 MΩ, ROK3 = 0.542 MΩ, ROV1 = 4.42 MΩ, ROV2 = 5.62 MΩ,
RUV1 = 3.83 MΩ, RUV2 = 6.12 MΩ, ROC1 = 10 MΩ, ROC2 = 10 MΩ
LBST
CSTOR
4.7µF
Battery(>100µF)
22µH
VSTOR
CHVR
4.7µF
1
16
15
LBST
VSTOR
`
14
13
VBAT
VSS
VSS
AVSS
12
VBAT_OK
Thermo electric
generator
2
ROC 2
10 MΩ
11
ROK1
bq25504
10 MΩ
ROC 1
VBAT_OK
VIN_DC
3
VOC_SAMP
4
VREF _SAMP
OK_PROG
CREF
0.01µF
OK_HYST
10
9
6
7
ROK2
6.12 MΩ
ROK3
OT_PROG VBAT_OV VRDIV VBAT _UV
5
3.32 MΩ
8
542kΩ
VSTOR
ROV2
5.62MΩ
ROV1
4.42MΩ
RUV 2
6.12MΩ
RUV 1
3.83MΩ
Figure 3. Typical TEG Application Circuit
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VIN_DC = 1.2 V, CSTOR = 4.7 µF, LBST = 22 µH, CHVR = 4.7 µF, TSD_PROTL (65°C),
MPPT (VOC) = Disabled VBAT_OV = 3.3 V, VBAT_UV = 2.2 V, VBAT_OK = 2.8 V, VBAT_OK_HYST = 3.1 V,
ROK1 = 3.97 MΩ, ROK2 = 5.05 MΩ, ROK3 = 0.976 MΩ, ROV1 = 5.56 MΩ,
ROV2 = 4.48 MΩ, RUV1 = 5.56 MΩ, RUV2 = 4.42 MΩ
LBST
CSTOR
4.7 µF
Primary Cell
Battery(>100 µF)
22 µH
VSTOR
CHVR
4. 7 µF
1
16
15
LBST
VSTOR
`
14
13
VBAT
VSS
VSS
12
AVSS
VBAT_OK
2
VBAT_OK
VIN_DC
11
ROK1
bq25504
VSTOR
3
VOC_SAMP
4
VREF_SAMP
3.97 MΩ
OK_PROG
OK_HYST
10
9
OT_PROG VBAT_OV VRDIV VBAT _UV
5
6
7
ROV2
4.48 MΩ
ROV1
5.56 MΩ
8
ROK2
5.05 MΩ
ROK3
976 kΩ
RUV2
4.42 MΩ
RUV1
5.56 MΩ
Figure 4. Typical MPPT Disabled Application Circuit
8
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HIGH-LEVEL FUNCTIONAL BLOCK DIAGRAM
LBST
VSTOR
VBAT
VSS
Boost Charge
Controller
AVSS
VSS
Cold-Start
Unit
VIN_DC
Enable
Enable
VBAT_OK
Interrupt
VOC_SAMP
OK_PROG
BAT_SAVE
MPPT
Controller
Vref
VREF_SAMP
OT
Battery Threshold
Control
OK
OK_HYST
UV
OV
Temperature
Sensing
Element
Vref
Bias Reference
and Oscillator
Vref
OT_PROG VBAT_OV
VRDIV
VBAT_UV
Figure 5. High-level Functional Diagram
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TYPICAL CHARACTERISTICS
Spacer
100
100
IIN = 10µA
90
80
80
70
70
Efficiency (%)
Efficiency (%)
90
60
50
40
30
60
50
40
30
20
VSTOR = 1.8V
VSTOR = 3V
VSTOR = 5.5V
10
0
−10
IIN = 100µA
VSTOR = 3.3 V
VSTOR = 1.8 V
VSTOR = 5.5 V
20
10
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Input Voltage (V)
G001
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Input Voltage (V)
G002
Figure 6. Efficiency vs Input Voltage
Figure 7. Efficiency vs Input Voltage
100
100
IIN = 10mA
VIN = 2V
90
90
Efficiency (%)
Efficiency (%)
80
70
60
50
40
VSTOR = 3V
VSTOR = 1.8V
VSTOR = 5.5V
30
20
80
70
60
VSTOR = 3V
VSTOR = 1.8V
VSTOR = 5.5V
50
40
0.01
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Input Voltage (V)
G003
Figure 8. Efficiency vs Input Voltage
0.1
1
Input Current (mA)
10
100
G004
Figure 9. Efficiency vs Input Current
90
90
VIN = 1V
VIN = 0.5V
80
80
Efficiency (%)
Efficiency (%)
70
70
60
60
50
40
50
40
0.01
0.1
1
Input Current (mA)
VSTOR = 3V
VSTOR = 1.8V
VSTOR = 5.5V
30
10
20
0.01
100
G005
Figure 10. Efficiency vs Input Current
10
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VSTOR = 3V
VSTOR = 1.8V
VSTOR = 5.5V
0.1
1
Input Current (mA)
10
100
G006
Figure 11. Efficiency vs Input Current
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TYPICAL CHARACTERISTICS (continued)
80
1000
VIN = 0.2V
900
800
VSTOR Current (nA)
Efficiency (%)
70
60
50
40
VSTOR = 3V
VSTOR = 1.8V
VSTOR = 5.5V
30
20
0.01
0.1
1
Input Current (mA)
10
700
600
500
400
300
VSTOR = 1.8V
VSTOR = 3V
VSTOR = 4V
200
100
0
−60
100
G007
Figure 12. Efficiency vs Input Current
−40
−20
0
20
40
60
Temperature (°C)
80
100
120
G008
Figure 13. VSTOR Quiescent Current vs Temperature
24
400
22
350
Time (ms)
Time (s)
20
18
16
300
250
14
200
12
10
−50−40−30−20−10 0 10 20 30 40 50 60 70 80 90 100
Temperature (°C)
G009
150
−50−40−30−20−10 0 10 20 30 40 50 60 70 80 90 100
Temperature (°C)
G010
Figure 14. Sample Period vs Temperature
Figure 15. Settling Period vs Temperature
VIN = 1 V, RIN = 20 W, VBAT = ramping power supply
VIN = 1 V, RIN = 20 W, VBAT = 100 µF capacitor
Figure 16. Example of Startup with no Battery and
10 KΩ Load
Figure 17. Example of VBAT_OK Operation, Ramping
Battery From 0 V to 3.1 V
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TYPICAL CHARACTERISTICS (continued)
VIN = 1 V, RIN = 20 W, VBAT = 3.1 V, RBAT = 100 mW
VIN = 1 V, RIN = 20 W, VBAT = 2.5 V, RBAT = 100 mW
Figure 18. Example of PFM Switching Converter Waveform
VIN = 1 V, RIN = 20 W, VBAT = 1.9 V, RBAT = 100 mW
VIN = 1 V, RIN = 20 W, VBAT = 3 V, RBAT = 100 mW
Figure 20. Example of Startup When VBAT is Held
Below UV Setting
12
Figure 19. Example of Output Ripple Voltage During
Operation at O V Setting
Figure 21. Example of Sampling Time for MPPT Operation
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DETAILED PRINCIPLE OF OPERATION
OPERATION
The bq25504 is an ultra low quiescent current, efficient synchronous boost converter/charger. The boost
converter is based on a switching regulator architecture which maximizes efficient operation while minimizing
start-up and operation power. The bq25504 uses pulse frequency mode (PFM) modulation to maintain efficiency,
even under light load conditions. In addition, bq25504 also implements battery protection features so that either
rechargeable batteries or capacitors can be used as energy storage elements. Figure 5 is a high-level functional
block diagram which highlights most of the major functional blocks inside the bq25504.
Boost Converter / Charger
Operation of the boost converter / charger begins when there is sufficient power available at the input pin
(VIN_DC) or available from an attached battery (VBAT) to raise the voltage at pin VSTOR above 1.8 V. The
start-up below 1.8 V on VSTOR of the boost-converter begins with the Cold-Start sub-system. If the VIN_DC is
greater than VSTOR or VBAT then current may flow until the voltage at the input is reduced or the voltage at
VSTOR and VBAT rise. This is considered an abnormal condition and the boost converter/charger does not
operate.
Cold -Start
The cold-start subsystem is used to turn on the device when the voltage present on pin VSTOR is < 1.8 V. Inside
the IC there is a switch (PMOS) between the energy storage capacitor VSTOR and the battery. If a battery is
initially attached to pin VBAT, the PMOS switch is momentary closed and any available charge from the battery
can be dumped onto VSTOR. If the resulting voltage is greater than about 1.8 V, then the bq25504’s biasing and
oscillator circuits can be turned on, and start up of the boost converter will be initiated. However, if there is
insufficient energy available in a connected battery, then the PMOS circuit is opened after ~20 ms, and the
cold-start sequence is initiated via power provided by power at the VIN_DC input pin.
When the voltage at pin VIN_DC exceeds the minimum input voltage with sufficient power, the cold start
subsystem turns on. When the storage capacitor voltage reaches 1.8 V the main boost regulator starts up. The
cold-start circuitry is then turned off after the voltage condition of VSTOR >1.8V and ~32 ms after input power
was applied. The output of the main boost regulator is now compared against battery undervoltage threshold
(VBAT_UV). When the VBAT_UVLO threshold is reached, the PMOS switch is turned on, which allows the
energy storage element attached to VBAT to charge up. Figure 22 shows the key threshold voltages. The battery
management thresholds are explained later is this section. Cold start is not as efficient as the main boost
regulator. If there is not sufficient power available it is possible that the cold start continuously runs and the
VSTOR output does not increase to 1.8 V and start the main boost regulator.
Boost Converter/Charger Operation
The boost converter in bq25504 is used to charge the storage element attached at VBAT with the energy
available from the DC input source. It employs pulse frequency modulation (PFM) mode of control to regulate the
input voltage (VIN_DC) close to the desired reference voltage. The reference voltage is set by the MPPT control
scheme as described in the next section. Input voltage regulation is obtained by transferring charge from the
input to VSTOR only when the input voltage is higher than the voltage on pin VREF_SAMP. The current through
the inductor is controlled through internal current sense circuitry. The peak current in the inductor is dithered
internally to set levels to maintain high efficiency of the converter across a wide input current range. The
converter nominally transfers up to a typical peak of 200 mA of input current. The boost converter is disabled
when the voltage on VSTOR reaches the OV condition to protect the battery connected at VBAT from
overcharging.
Maximum Power Point Tracking
Maximum power point tracking (MPPT) is implemented in bq25504 in order to maximize the power extracted
from an energy harvester source. MPPT is performed by periodically sampling a ratio of the open-circuit voltage
of the energy harvester and using that as the reference voltage (VREF_SAMP) to the boost converter. The
sampling ratio can be externally programmed using the resistors ROC1 and ROC2. For solar harvesters, the
resistive division ratio can be typically set between 0.7-0.8 and for thermoelectric harvesters; a resistive division
ratio of 0.5 is typically used. The exact ratio for MPPT can be optimized to meet the needs of the input source
being used.
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Internally, the boost converter modulates the effective impedance of the energy transfer circuitry to regulate the
input voltage (VIN_DC) to the sampled reference voltage (VREF_SAMP). A new reference voltage is obtained
every 16s by periodically disabling the charger for 256ms and sampling a ratio of the open-circuit voltage. The
reference voltage is set by the following expression:
æ
ö
R OC1
VREF_SAMP = VIN_DC(OpenCircuit) ç
÷
è R OC1 + R OC2 ø
(1)
The internal MPPT circuitry and the periodic sampling of VIN_DC can be disabled by tying the VOC_SAMP pin
to VSTOR. When disabled an external reference voltage can be fed to the VREF_SAMP pin. The boost
converter will then regulate VIN_DC to the externally provided reference. If input regulation is not desired,
VREF_SAMP can be tied to GND.
Storage Element
The storage elements should be connected to VBAT pin. Many types of elements can be used, such as
capacitors, super capacitors or various battery chemistries. If a capacitor is selected it needs to meet the
minimum capacitance of 100 µF. If a battery is used it should be selected to have a minimum capacity equivalent
to 100 µF capacitance. To take full advantage of the battery management, the load is normally tied to the
VSTOR pin. Also, if there is large load transients or the storage element has impedance then it is necessary to
add a low ESR by-pass capacitor to prevent a droop in voltage.
Battery Management
In this section the battery management functionality of the bq25504 integrated circuit (IC) is presented. The IC
has internal circuitry to manage the voltage across the storage element and to optimize the charging of the
storage element. For successfully extracting energy from the source, three different threshold voltages must be
programmed using external resistors, namely the under voltage (UV) threshold, battery good threshold
(VBAT_OK) and over voltage (OV) threshold. The three threshold voltages determine the region of operation of
the IC. Figure 22 shows a plot of the voltage at the VSTOR pin and the various threshold voltages. For the best
operation of the system, the VBAT_OK should be used to determine when a load can be applied or removed. A
detailed description of the three voltage thresholds and the procedure for designing the external resistors for
setting the three voltage thresholds are described next.
device absolute max = 5.5 V
Charger off
over voltage (user programmable) = 3.1 V
Increasing VSTOR voltage
over voltage – hyst (internal)
VBAT_OK + hyst (user programmable) = 2.8 V
VBAT_OK (user programmable) = 2.4 V
Main Boost
Charger on
under voltage + hyst (internal)
under voltage (user programmable) = 2.2 V
charger enable = 1.8 V
chip enable = 1.4 V
Cold start
ground
Figure 22. Figure Shows the Relative Position of Various Threshold Voltages
(Threshold Voltages are From Typical Solar Application Circuit in Figure 2)
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Battery Undervoltage Protection
To prevent rechargeable batteries from being deeply discharged and damaged, and to prevent completely
depleting charge from a capacitive storage element, the undervoltage (VBAT_UV) threshold must be set using
external resistors. The VBAT_UV threshold voltage when the battery voltage is decreasing is given by
Equation 2:
æ
ö
R
VBAT_UV = VBIAS ç 1 + UV2 ÷
R UV1 ø
è
(2)
The sum of the resistors must be 10 MΩ i.e., RUV1 + RUV2 = 10 MΩ. The undervoltage threshold when battery
voltage is increasing is given by UV_HYST. It is internal set to the under voltage threshold plus an internal
hysteresis voltage denoted by VBAT_UV_HYST. For proper functioning of the IC and the overall system, the
load must be connected to the VSTOR pin while the storage element must be connected to the VBAT pin. Once
the VSTOR pin voltage goes above the UV_HYST threshold, the VSTOR pin and the VBAT pins are shorted.
The switch remains closed until the VSTOR pin voltage falls below the under voltage threshold. The VBAT_UV
threshold should be considered a fail safe to the system and the system load should be removed or reduced
based on the VBAT_OK signal.
Battery Overvoltage Protection
To prevent rechargeable batteries from being exposed to excessive charging voltages and to prevent over
charging a capacitive storage element, the over-voltage (VBAT_OV) threshold level must be set using external
resistors. This is also the voltage value to which the charger will regulate the VSTOR/VBAT pin when the input
has sufficient power. The VBAT_OV threshold when the battery voltage is rising is given by Equation 3:
æ
ö
R
3
VBAT_OV = VBIAS ç 1 + OV2 ÷
2
R OV 1 ø
è
(3)
The sum of the resistors must be 10 MΩ i.e. ROV1 + ROV2 = 10 MΩ. The overvoltage threshold when battery
voltage is decreasing is given by OV_HYST. It is internal set to the over voltage threshold minus an internal
hysteresis voltage denoted by VBAT_OV_HYST. Once the voltage at the battery exceeds VBAT_OV threshold,
the boost converter is disabled. The charger will start again once the battery voltage falls below the
VBAT_OV_HYST level. When there is excessive input energy, the VBAT pin voltage will ripple between the
VBAT_OV and the VBAT_OV_HYST levels.
CAUTION
It should also be noted that if VIN_DC is higher than VSTOR and VSTOR is higher
than VBAT_OV, the input VIN_DC is shorted to ground to stop further charging of the
attached battery or capacitor. It is critical that if this case is expected, the source
impedance on VIN_DC is made higher than 20 Ω, it must not be a low impedance
source.
Battery Voltage in Operating Range (VBAT_OK Output)
The IC allows the user to set a programmable voltage independent of the overvoltage and undervoltage settings
to indicate whether the battery voltage is at an acceptable level. When the battery voltage is decreasing the
threshold is by Equation 4
æ
ö
R
VBAT_OK_PROG = VBIAS ç 1 + O K2 ÷
R OK1 ø
è
(4)
When the battery voltage is increasing, the threshold is by Equation 5
æ
R
+ R O K3 ö
VBAT_OK_HYST = VBIAS ç 1 + OK2
÷
R O K1
è
ø
(5)
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The sum of the resistors must be 10 MΩ i.e., ROK1 + ROK2 + ROK3= 10 MΩ. The logic high level of this signal is
equal to the VSTOR voltage and the logic low level is ground. The logic high level has ~20 KΩ internally in series
to limit the available current to prevent MCU damage until it is fully powered. The VBAT_OK_PROG threshold
must be greater than or equal to the UV threshold. For the best operation of the system, the VBAT_OK should
be setup to determine when a load can be applied or removed to optimize the storage element capacity.
Thermal Shutdown
Rechargeable Li-ion batteries need protection from damage due to operation at elevated temperatures. The
application should provide this battery protection and ensure that the ambient temperature is never elevated
greater than the expected operational range of 85°C.
The bq25504 uses an integrated temperature sensor to monitor the junction temperature of the device. If the
OT_PROG pin is tied low then the temperature threshold for thermal protection is set to TSD_ProtL which is
65°C typically. If the OT_PROG is tied high, then the temperature is set to TSD_ProtH which is 120°C typically.
Once the temperature threshold is exceeded, the boost converter/charger is disabled and charging ceases. Once
the temperature of the device drops below this threshold, the boost converter/charger can resume operation. In
order to avoid unstable operation near the overtemp threshold, a built-in hysteresis of approximately 5°C has
been implemented. Care should be taken to not over discharge the battery in this condition since the boost
converter/charger is disabled. However, if the supply voltage drops to the VBAT_UV setting, then the switch
between VBAT and VSTOR will open and protect the battery even if the device is in thermal shutdown.
APPLICATION INFORMATION
INDUCTOR SELECTION
For the bq25504 to operate properly, an inductor of appropriate value must be connected between Pin # 16
(LBST) and Pin #2 (VIN_DC) for the boost converter.
For the boost converter / charger, the inductor must have an inductance = 22 µH and have a peak current
capability of ≥250 mA with the minimum series resistance to keep high efficiency.
CAPACITOR SELECTION
In general, all the capacitors need to be low leakage. Any leakage the capacitors have will reduce efficiency,
increase the quiescent current and diminish the effectiveness of the IC for energy harvesting.
Sampled Reference Storage Capacitance:
The MPPT operation depends on the sampled value of the open circuit voltage and the input regulation follows
the voltage stored on the CREF capacitor. This capacitor is very sensitive to leakage since the holding period is
around 16 seconds. As the capacitor voltage drops due to any leakage, the input regulation voltage will also drop
and this can prevent proper operation from extraction the maximum power from the input source. Therefore, it is
recommended that the leakage be less than 2 nA at 3 V bias.
Input capacitor:
Operation of the BQ25504 requires a capacitor to be connected between Pin 15 (VSTOR) and ground. A
capacitor of 4.7 µF should be connected between Pin 15 and ground to assure stability of the boost converter,
especially when the battery is fully charged and the converter in output voltage limiting mode.
Energy from the energy harvester input source is initially stored on a capacitor CHVR tied to Pin 2 (VIN_DC) and
ground (VSS, Pin 1). For energy harvesters which have a source impedance which is dominated by a capacitive
behavior, the value of the harvester capacitor should scaled according to the value of the output capacitance of
the energy source , but an initial value of 4.7 µF is recommended.
16
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Storage capacitor:
An additional storage capacitor CBAT, either stand-alone, or in parallel with the battery should be attached
between Pin 14 (VBAT) and GND. The value of this capacitor should be selected to meet the needs of any load
attached to the battery. For instance, some Li-ion batteries or thin-film batteries may not have the current
capacity to meet the surge current requirements of an attached low power radio. Therefore, adding a capacitor
may help buffer this load and provide the brief current surge needs.
Additionally, when the system load has large transients, adding a small high frequency capacitor in parallel to
CSTOR may help buffer this load and provide the brief current surge needs.
For a recommend list of standard components, please see the EVM User’s guide.
LAYOUT CONSIDERATIONS
As for all switching power supplies, the layout is an important step in the design, especially at high peak currents
and high switching frequencies. If the layout is not carefully done, the boost converter/charger could show
stability problems as well as EMI problems. Therefore, use wide and short traces for the main current path and
for the power ground paths. The input and output capacitor, as well as the inductor should be placed as close as
possible to the IC.
The resistors that program the thresholds should be placed as close as possible to the input pins of the IC to
minimize parasitic capacitance to less than 2 pF.
To layout the ground, it is recommended to use short traces as well, separated from the power ground traces.
This avoids ground shift problems, which can occur due to superimposition of power ground current and control
ground current. Assure that the ground traces are connected close to the device GND pin.
THERMAL CONSIDERATIONS
Implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requires
special attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, added
heat sinks and convection surfaces, and the presence of other heat-generating components affect the
power-dissipation limits of a given component.
Three basic approaches for enhancing thermal performance are listed below.
• Improving the power-dissipation capability of the PCB design
• Improving the thermal coupling of the component to the PCB
• Introducing airflow in the system
For more details on how to use the thermal parameters in the Thermal Table, check the Thermal Characteristics
Application Note (SZZA017) and the IC Package Thermal Metrics Application Note (SPRA953).
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PACKAGE OPTION ADDENDUM
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17-Oct-2011
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
Pins
Package Qty
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
BQ25504RGTR
ACTIVE
QFN
RGT
16
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
BQ25504RGTT
ACTIVE
QFN
RGT
16
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Samples
(Requires Login)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
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in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
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Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Oct-2011
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
BQ25504RGTR
QFN
RGT
16
3000
330.0
12.4
3.3
3.3
1.1
8.0
12.0
Q2
BQ25504RGTT
QFN
RGT
16
250
180.0
12.4
3.3
3.3
1.1
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Oct-2011
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
BQ25504RGTR
QFN
RGT
16
3000
346.0
346.0
29.0
BQ25504RGTT
QFN
RGT
16
250
210.0
185.0
35.0
Pack Materials-Page 2
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Copyright © 2011, Texas Instruments Incorporated
User's Guide
SLUU654A – October 2011 – Revised October 2011
bq25504 EVM – Ultra Low Power Boost Converter with
Battery Management for Energy Harvester Applications
This user’s guide describes the bq25504 evaluation module (EVM), how to perform a stand-alone
evaluation and allows the EVM to interface with the system and host. This EVM is programmed from the
factory for settings compatible with most MCU’s and 3V coin cell batteries. The EVM is programmed to
deliver a 3.1VDC maximum voltage (OV) for charging the storage element and the under voltage is
programmed to 2.2VDC. The VBAT_OK indicator toggles high when VSTOR ramps up to 2.8VDC and
toggles low when VSTOR ramps down to 2.4VDC.
1
2
3
4
5
Contents
Introduction .................................................................................................................. 2
1.1
EVM Features ...................................................................................................... 2
1.2
General Description ................................................................................................ 2
1.3
Design and Evaluation Considerations .......................................................................... 3
Performance Specification Summary ..................................................................................... 4
Test Summary ............................................................................................................... 4
3.1
Equipment ........................................................................................................... 4
3.2
Equipment and EVM Setup ....................................................................................... 4
3.3
Test procedures .................................................................................................... 5
PCB Layout Guideline .................................................................................................... 11
Bill of Materials, Board Layout and Schematics ....................................................................... 12
5.1
Bill of Materials .................................................................................................... 12
5.2
EVM Board Layout ............................................................................................... 13
5.3
EVM Schematic ................................................................................................... 15
List of Figures
1
Test Setup for HPA674A (bq25504 EVM) ............................................................................... 5
2
Startup with no Battery and 10k Load .................................................................................... 6
3
Startup with Battery Less Than UV ....................................................................................... 7
4
Powering up with a Battery above UV
5
6
7
8
9
10
11
...................................................................................
BAT_OK High/Low 2.8V/2.34V – Ramping Battery from 0V to 3.1V (OV) and Down to 1.8V. ...................
Basic Switching Converter, Vin = 1V, Vbat = 2.5V .....................................................................
EVM Operation Near OV With 100-Ω Battery Impedance ...........................................................
EVM PCB Top Assembly .................................................................................................
EVM PCB Top Layer .....................................................................................................
EVM PCB Bottom Layer ..................................................................................................
EVM Schematic ............................................................................................................
7
8
9
10
13
13
14
15
List of Tables
1
I/O Connections and Configuration for Evaluation of bq25504 EVM................................................. 4
2
Bill of Materials............................................................................................................. 12
SLUU654A – October 2011 – Revised October 2011
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bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for
Energy Harvester Applications
Copyright © 2011, Texas Instruments Incorporated
1
Introduction
1
Introduction
1.1
EVM Features
•
•
•
•
•
•
1.2
www.ti.com
Evaluation module for bq25504
Ultra low power boost converter/charger with battery management for energy harvester applications
Resistor-programmable settings for under voltage, over voltage providing flexible battery management;
POTs Included for fine tuning the settings (not populated)
Programmable push-pull output Indicator for battery status (VBAT_OK)
Test points for key signals available for testing purpose – easy probe hook-up.
Jumpers available – easy to change settings
General Description
The bq25504 is the first of a new family of intelligent integrated energy harvesting Nano-Power
management solutions that are well suited for meeting the special needs of ultra low power applications.
The product is specifically designed to efficiently acquire and manage the microwatts (µW) to miliwatts
(mW) of power generated from a variety of DC sources like photovoltaic (solar) or thermal electric
generators. The bq25504 is the first device of its kind to implement a highly efficient boost
converter/charger targeted toward products and systems, such as wireless sensor networks (WSN) which
have stringent power and operational demands. The design of the bq25504 starts with a DC-DC boost
converter/charger that requires only microwatts of power to begin operating. Once started, the boost
converter/charger can effectively extract power from low voltage output harvesters such as thermoelectric
generators (TEGs) or single / dual cell solar panels. The boost converter can be started with VIN as low
as 330 mV typ., and once started, can continue to harvest energy down to VIN ≃ 100 mV.
The bq25504 also implements a programmable maximum power point tracking (MPPT) sampling network
to optimize the transfer of power into the device. The MPP is listed by the harvesting manufacturer as a
percentage of its open circuit (OC) voltage. Typically solar cells are at their MPP when loaded to ~80% of
their OC voltage. The bq25504 periodically samples the open circuit input voltage by disabling the boost
converter (approximately every 16 seconds) and stores the programmed MPP ratio of the OC voltage on
the external reference capacitor, C5. If the storage element is less than the maximum voltage (OV) then
the boost converter will load the harvesting source until it reaches the MPP (C5 voltage reference) and
then regulate the input voltage of the converter, thus transferring the maximum amount of power to the
output. Alternatively, an external reference voltage can be provided, by a MCU to the REFS pin, to adjust
C5 independently. The shunt on JP1 has to be moved from the Divider setting to STOR when providing
this external reference (JP1-2 tied to JP1-1 – OSC/STOR).
The bq25504 was designed with the flexibility to support a variety of energy storage elements. The
availability of the sources from which harvesters extract their energy can often be sporadic or
time-varying. Systems will typically need some type of energy storage element, such as a re-chargeable
battery, super capacitor, or conventional capacitor. The storage element will make certain constant power
is available when needed for the systems. The storage element also allows the system to handle any peak
currents that can not directly come from the input source.
To prevent damage to a customer’s storage element, both maximum and minimum voltages are monitored
against the user programmed under-voltage (UV) and over-voltage (OV) levels.
To further assist users in the strict management of their energy budgets, the bq25504 toggles the battery
good flag to signal the microprocessor when the voltage on an energy storage element or capacitor has
dropped below a pre-set critical level. This should trigger the shedding of load currents to prevent the
system from entering an under voltage condition.
The OV, UV and battery good thresholds are programmed independently. The EVM has three 500KΩ
potentiometers (not installed at factory) to allow fine tuning of the three programmable thresholds. This
only need be done if the user needs precision, the POTs provide about ±50mV shift.
For details, see bq25504 data sheet (SLUSAH0).
2
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
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Introduction
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1.3
Design and Evaluation Considerations
This user's guide is not a replacement for the data sheet. Reading the data sheet first will help in
understanding the operations and features of this IC. Be sure to make note of the capacitor selection
section when designing the EVM. Many of the IC's pin names start with a "V" and this "V" is removed on
the EVM connector's label. The names are interchangeable.
This IC is a highly efficient charger for a storage element such as a battery or super capacitor. In this
document, “battery” will be used but one could substitute any appropriate storage element. The main
difference between a battery and a super capacitor is the capacity curve. The battery typically has little or
no capacity below a certain voltage, where as the capacitor does have capacity at lower voltages.
In the lab when using a lab power supply rather than an energy harvester, one will have the output of the
lab supply, Vsource, followed by the harvester's impedance (about 20Ω) and connected to VIN of the EVM.
These two signals are separated by the 20Ω source impedance which represents the internal impedance
of the source. VIN is equal to VSource when there is no load (open circuit) and is pulled down to the MPPT
harvester threshold when the charger is able to deliver the maximum power before reaching OV.
The over voltage (OV) setting initially is lower than the programmed value at startup (varies on conditions)
and is updated after the first ~32ms. Subsequent updates are every ~64ms. The OV threshold is the
reference for maximum voltage on VSTOR and the boost converter will stop switching if the voltage on
VSTOR reaches the OV reference. The UV is checked every ~64ms to determine if the BAT FET should
be on or off. The open circuit (OC) input voltage is measured every ~16 seconds which is used to
calculate the Maximum Power Point Tracking (MPPT) threshold (programmed with resistors to 78% at the
factory). This periodic update continually optimizes maximum power delivery based on the harvesting
conditions.
Harvesting ultra low power energy requires a different mind set when designing a system. Often there is
not enough real time input harvested power to run the system in full operation so energy is collected over
a period of time, stored in a battery and then used periodically to power the system.
The designer needs to define a “Battery OK” threshold and battery discharged threshold (Not OK) to allow
successful system operation. The BAT_OK high/low threshold are programmed at the factory to 2.8V and
2.4V using resistors R7, R8, and R9. A BAT_OK high signal would typically indicate to the host that the
battery is above 2.8V and ready to use and if low would indicate that the cell is discharged such that the
system load should be reduced or disabled. The BAT_OK signal is checked every 64ms.
The quiescent current, which is basically the current from the battery to the IC, can be measured at the
STOR pin. To measure the current the user should connect a 100kΩ resistor to J5-2 (STOR) and connect
a 3V supply from the other end of this resistor to the ground of the EVM. A 10MΩ meter can be used to
measure the voltage drop across the resistor and calculate the current. No other connections should be
made to the EVM and the measurement should be taken after steady state conditions are reached (may
take a few minutes). The reading should be in the range of 375nA.
The battery (storage element) can be replaced with a simulated battery. Often electronic 4 quadrant loads
give erratic results with a “battery charger” due to the charger changing states (fast-charge to termination
and refresh) while the electronic load is changing loads to maintain the “battery” voltage. The charging and
loading get out of phase and creates a large signal oscillation which is due to the 4 quadrant meter. A
simple circuit can be used to simulate a battery and works well and can quickly be adjusted for voltage. It
consists of load resistor (~10Ω, 2W) to pull the output down to some minimum storage voltage (sinking
current part of battery) and a lab supply connected to the BAT pin via a diode. The lab supply biases up
the battery voltage to the desired level. It may be necessary to add more capacitance across R1.
D1
C
A
BAT+
R1
GND
SLUU654A – October 2011 – Revised October 2011
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3
Performance Specification Summary
2
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Performance Specification Summary
See Data Sheet “Recommended Operating Conditions” for component adjustments. For details about the
resistor programmable settings, see bq25504 data sheet (SLUSAH0).
MIN
NOM
VIN(DC)
DC input voltage into VIN_DC
DC minimum Start-up Voltage
VOV
Over Voltage – Sets maximum output voltage
2.9
3.1
3.3
V
VUV
Under voltage setting for shorting VSTOR to VBAT
2.1
2.2
2.3
V
VBAT_OK indication toggles high when VSTOR ramps up
2.65
2.8
2.95
V
VBAT_OK indication toggles low when VSTOR ramps down
2.25
2.4
2.55
V
330
MPPT
Maximum Power Point Tracking, Programmed % of Open Circuit Voltage
CBAT
Battery Pin Capacitance or equivalent battery capacity
3
Test Summary
3.1
Equipment
3.0
UNIT
VIN_Start-up(DC)
VBAT_OK
0.13
MAX
V
mV
78%
100
µF
Power Supplies
Power Supply #1 (PS#1): Adjustable 5V Power supply with Current Limit of 100mA.
Power Supply #2 (PS#2): Adjustable 5V Power supply with 20Ω series impedance (can just be a discrete
resistor) with Current Limit of 100mA.
Loads
Load #1: 10kΩ, 5%, 0.25W resistor and 1kΩ, 5%, 0.25W resistor as per procedure P/S#2 series
resistance: 20Ω, 5%, 0.25W
Meters
Meter#1,2,3: Fluke 75 multi-meter, (equivalent or better) for voltage measurements
Scope
Standard scope with at least two channels
3.2
Equipment and EVM Setup
Table 1. I/O Connections and Configuration for Evaluation of bq25504 EVM
4
Jack
Description
Factory Setting
J1–VIN
Input Source (+)
J1–GND
Input Source Return (–)
J2–BAT
Battery connection (+)
J2–GND
Battery Connection Return (–)
J3 – VIN
Input Source Sense (+) [for J1]
J3 -GND
Input Source Return Sense (–) [for J1]
J4 – BAT_OK
Battery Status Indicator (+)
J4 - GND
Battery Status Indicator Return (–)
J5 – STOR
Charger Output (+)
J5 – GND
Charger Output Return (–)
J6 – STOR
Charger Output Sense (+)
J6 – BAT
Battery Connection Sense (+) [for J2]
J6 - GND
Battery Connection Sense (–) [for J2]
JP1
MPPT setting: Enabled-Divider; Disabled-STOR
Place Shunt on JP1-2/3 (Divider)
JP2
OCS Setting: C5 Capacitor-No Shunt; Disabled-Shunt on REF-GND
(JP1 should be Disabled)
No Shunt
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for
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Test Summary
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Load # 1
_
Meter # 4
+
Meter # 2
-
+
Meter # 3
+
-
-
+
Meter # 1
P/S # 1
+
-
Jumper
Figure 1. Test Setup for HPA674A (bq25504 EVM)
3.3
3.3.1
Test procedures
Power-up With No Battery and 10kΩ Load on STOR
1. Connect a 20Ω resistor to J1-1, 10k resistor between J6-1 and J6-3 and place shunt on JP1-DIV.
Connect meters and scope probes to monitor CH1→CH4: VPHASE(TP16), VSTOR, VP/S #1, VBAT. Set scope
to 1V per division for each channel and 20ms/div, single sequence trigger on VP/S#1, see Figure 2.
2. Set PS#1 to 1VDC and hot plug to input with 20Ω series resistor.
This is an example of cold startup (VSTOR < 1.8V). The input power is harvested by the boost converter and
charges up to the initial OV setting, which is below the actual setting (pseudo softstart), the converter
stops switching and the load discharges the STOR capacitor. Note that if the load is too great with no
battery or a discharge battery the cold start may not be able to charge the battery. Therefore, it is
important to manage the load with a discharged or missing battery, using BAT_OK. The converter
continues to switch until VSTOR charges up to the OV threshold at 3.1V, the converter shuts off until VSTOR
drops 35 mV (hysteresis) below OV and then the converter switches on periodically to maintain the output
voltage. This is a similar operation to a hysteretic boost converter.
VPHASE is the inductor switching node.
SLUU654A – October 2011 – Revised October 2011
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Test Summary
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Vstor
Vbat
Vphase
Vp/s#1
Figure 2. Startup with no Battery and 10k Load
3.3.2
Power-up with Battery less than UV (less than a diode drop below UV)
1. Same setup, as 3.3.1, except move the probe on VBAT to VIN and apply a charge element set to 1.9VDC
between BAT and GND. Arm scope to trigger on VP/S #1.
2. Set PS#1 to 1VDC and hot plug to input with 20Ω series resistor, see Figure 3.
The start up is similar to the case without the battery but after the initial ~40ms period the STOR charges
to 2.8V or ~0.9V above the battery and is charging the element via the BAT FET body diode. The next
sampling cycle for UV detects that the VSTOR is greater than UV (2.2V) and then turns on the BAT FET.
Since the battery is at 1.9V, VSTOR is pulled down to ~1.9V and the next UV sampling turns off the BAT
FET. The cycling continues until the battery gets charged to the UV threshold and then finally the BAT
FET stays on. A less complicated design would turn off the system load once the battery drops near the
UV threshold to avoid this cycling.
If the storage element is lower than the maximum voltage (OV) then the element can theoretically take all
of the available input power. As the harvesting source is loaded, its output voltage drops until reaching the
MPPT threshold, which is currently programmed to 78% of the OC voltage and then the boost converter
regulates the input voltage at this level by controlling the power transferred to the load. Note how Vin
regulates to 78% of P/S#1 when the battery is lower than the OV voltage. Vary the input voltage slightly
and wait for the 16 second update cycle to see how the MPPT is updated.
For a battery that is more than a diode drop below 1.8V, the charger may get stuck in cold startup which is
less efficient and would take longer to recover. Once the STOR voltage gets above 1.8V and more than
32ms after power is applied, the low power cold start circuit is disabled and the main boost converter
takes over.
6
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
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Test Summary
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Vstor
Vin
Vp/s#1
Vphase
Figure 3. Startup with Battery Less Than UV
3.3.3
Power-up with Battery more than UV (2.3V to 3V), BAT FET ON
1. Same setup as 3.3.1, except change the charge element set to 2.4VDC between BAT and GND. Set
scope to 2sec/div and to roll.
2. Set PS#1 to 1VDC and hot plug to input with 10Ω series resistor, see Figure 4.
Note in Figure 4 that the BAT FET is on and the STOR output is powered prior to the input being applied.
This means the converter will start up in normal boost mode and after doing its initial sampling will
regulate VIN to the MPPT threshold.
Vstor
Vp/s#1
Vin
Vphase
Figure 4. Powering up with a Battery above UV
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Test Summary
3.3.4
www.ti.com
BAT_OK Indication as Battery Charges/Discharges
1. Connect scope probes CHI→CH4: VPHASE(TP16), VSTOR, VBAT_OK, VBAT and vary charge element from
zero voltage to 3.15V and back down to 1.8V and observe the BAT_OK signal.
Initially P/S#1 is set to 1V and the battery is adjusted to OV (simulated battery), which clamps VSTOR to
~0.5V (lower body diode drop due to lower current). As the battery voltage is swept higher one can see
the different phases discussed earlier. Once the output gets to ~2.8V the BAT_OK signal goes high. Note
that the BAT_OK signal goes low once the battery is discharged to ~2.34V.
This signal’s high and low threshold can be programmed by R7, R8 and R9 to give an indication to the
host when the battery is good (Signal high – has enough energy to complete the designed task) and when
the battery is discharged (Signal low – system needs to be disabled or low power mode so the battery can
recharge).
V_BAT-OK
Vstor Vbat
Vphase
Figure 5. BAT_OK High/Low 2.8V/2.34V – Ramping Battery from 0V to 3.1V (OV) and Down to 1.8V.
3.3.5
Basic PFM Switching Waveform, Vin = 1V, Vbat = 2.5V
1. Set up scope as follows: CHI→CH4: VPHASE(TP16), VSTOR, VP/S #1, VIN, 10µs/DIV.
8
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
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Test Summary
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Vstor
Vsource
Vin
Vphase
Figure 6. Basic Switching Converter, Vin = 1V, Vbat = 2.5V
Note here that VIN is regulating at the MPPT threshold so the boost circuit is delivering the maximum
power that the source can deliver. The user can see after about 4 pulses that the switching waveforms
stops which cause the inductor to go discontinuous and ring.
SLUU654A – October 2011 – Revised October 2011
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Test Summary
3.3.6
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Operation Near OV With 100-Ω Battery Impedance
1. Connect scope probes CHI→CH4: VPH(TP16), VSTOR, VIN, VBAT; set VP/S#1 to 1.3 VDC and VBAT to 3.00
VDC. Connect the power sources with their respective source impedance to the EVM. VIN source
impedance should be 20Ω and the battery impedance should be 100Ω. Set VSTOR and VBAT to
20mVDC/div and 3.135VDC offset (3.135VDC was the average VBAT [OV] measurement), 1 ms/div.
Turn on sources.
2. The input source has enough energy to charge the VSTOR up to the OV setting; and. when the boost
converter stops switching VSTOR will discharge down to the battery’s cell voltage which is ~3V which is
below the OV reset hysteresis. See Figure 7 for operation near OV. Note the hysteresis of VSTOR is
around 35mV here, but this can vary depending on the input, output voltage, the source and battery
impedance, and the number of pulses for each operation period of the boost converter.
Vstor
Vbat
Vin
Vphase
Figure 7. EVM Operation Near OV With 100-Ω Battery Impedance
10
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
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PCB Layout Guideline
www.ti.com
4
PCB Layout Guideline
1. As with all switching power supplies, the layout is an important step in the design, especially at high
peak currents and high switching frequencies. If the layout is not carefully done, the boost
converter/charger could show stability problems as well as EMI problems. Therefore, use wide and
short traces for the main current path and for the power ground paths. The input and output capacitor,
as well as the inductor should be placed as close as possible to the IC.
2. The resistors that program the thresholds should be placed as close as possible to the input pins of the
IC to minimize parasitic capacitance to less than 2pF.
3. To lay out the ground, it is recommended to use short traces as well, separated from the power ground
traces. This avoids ground shift problems, which can occur due to superimposition of power ground
current and control ground current. Assure that the ground traces are connected close to the device
GND pins.
4. It is critical that the exposed thermal pad on the backside of the bq25504 package be soldered to the
PCB ground. Make sure there are sufficient thermal vias right underneath the IC, connecting to the
ground plane on the other layers.
5. Decoupling capacitors for VSTOR, VBAT should make the interconnections to the any Load as short
as possible.
6. EVM layout can be used as guidance though a smaller layout is achievable.
SLUU654A – October 2011 – Revised October 2011
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11
Bill of Materials, Board Layout and Schematics
www.ti.com
5
Bill of Materials, Board Layout and Schematics
5.1
Bill of Materials
Table 2. Bill of Materials
Count
RefDes
Value
Description
Size
Part Number
MFR
2
C1, C2**
4.7uF
Capacitor, Ceramic, 10V, X5R, 10%
0805
GRM219R61A475KE19D
Murata
1
C3**
100uF
Capacitor, Ceramic, 6.3V, X5R, 20%
1812
GRM43SR60J107ME20L
Murata
2
C4, C6
0.1uF
Capacitor, Ceramic, 50V, X7R, 10%
0603
Std
Std
1
C5**
0.01uF
Capacitor, Ceramic, 50V, X7R, 10%
0603
GRM188R71H103KA01D
Murata
3
J1, J2, J5
ED555/2DS
Terminal Block, 2-pin, 6-A, 3.5mm
0.27 x 0.25
inch
ED555/2DS
OST
2
J3, J4
PEC02SAAN
Header, Male 2-pin, 100mil spacing,
0.100 inch x 2
PEC02SAAN
Sullins
1
J6
PEC03SAAN
Header, Male 3-pin, 100mil spacing,
0.100 inch x 3
PEC03SAAN
Sullins
2
JP1, JP2
PEC03SAAN
Header, Male 3-pin, 100mil spacing,
0.100 inch x 3
PEC03SAAN
Sullins
1
L1
22uH
Inductor, SMT, 0.8A, 360milliohm
0.153 x 0.153
inch
LPS4018-223MLB
Coilcraft
1
R1
10.0M
Resistor, Chip, 1/10W, 1%
0805
CRCW080510M0FKEA
Vishay
0
R11
Open
Resistor, Chip, 1/10W, 1%
0805
Std
Std
4
R12, R14, R15,
R16
0
Resistor, Chip, 1/10W, 1%
0805
Std
STD
0
R13, R17, R18
Open
Potentiometer, 1/4 in. Cermet, 12-Turn,
Top-Adjust
0.25x0.17
3266W-504LF
Bourns
3
R2, R6, R8
4.42M
Resistor, Chip, 1/10W, 1%
0805
CRCW08054M42FKEA
Vishay
1
R3
5.90M
Resistor, Chip, 1/10W, 1%
0805
CRCW08055M90FKEA
Vishay
1
R4
4.02M
Resistor, Chip, 1/10W, 1%
0805
CRCW08054M02FKEA
Vishay
2
R5, R10
5.60M
Resistor, Chip, 1/10W, 1%
0805
CRCW08055M60FKEA
Vishay
1
R7
1.43M
Resistor, Chip, 1/10W, 1%
0805
CRCW08051M43FKEA
Vishay
1
R9
4.22M
Resistor, Chip, 1/10W, 1%
0805
CRCW08054M22FKEA
Vishay
0
TP1, TP2, TP6,
TP7, TP8, TP9,
TP10, TP14,
TP16, TPG1,
TPG2, TPG3,
TPG4
Open
Test Point, O.032 Hole
STD
STD
1
U1
BQ25504RGT
IC, NanoAmpere Integrated Boost
Converter/Charger
QFN-16
BQ25504RGT
TI
HPA674
Any
0.1
929950-00
3M
1
--
PCB, 1.8 In x 1.8 In x 0.031 In
2
See Note 5
Shunt, 100-mil, Black
Notes: 1. These assemblies are ESD sensitive, ESD precautions shall be observed.
2. These assemblies must be clean and free from flux and all contaminants. Use of no clean flux is not acceptable.
3. These assemblies must comply with workmanship standards IPC-A-610 Class 2.
4. Ref designators marked with an asterisk ('**') cannot be substituted. All other components can be substituted with equivalent MFG's components.
5. Place shunt on JP1-2/3 (Divider) and JP2 (place on just one pin – ckt should be floating).
12
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
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Bill of Materials, Board Layout and Schematics
www.ti.com
5.2
EVM Board Layout
TEXAS
INSTRUMENTS
Figure 8. EVM PCB Top Assembly
Figure 9. EVM PCB Top Layer
SLUU654A – October 2011 – Revised October 2011
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bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for
Energy Harvester Applications
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13
Bill of Materials, Board Layout and Schematics
www.ti.com
Figure 10. EVM PCB Bottom Layer
14
bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for SLUU654A – October 2011 – Revised October 2011
Energy Harvester Applications
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Copyright © 2011, Texas Instruments Incorporated
Bill of Materials, Board Layout and Schematics
www.ti.com
5.3
EVM Schematic
Figure 11. EVM Schematic
SLUU654A – October 2011 – Revised October 2011
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bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for
Energy Harvester Applications
Copyright © 2011, Texas Instruments Incorporated
15
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This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION
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EVM Warnings and Restrictions
It is important to operate this EVM within the input voltage range of 0 V to 5.5 V and the output voltage range of 0 V to 5.5 V .
Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If there are
questions concerning the input range, please contact a TI field representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/or possible permanent damage to the
EVM. Please consult the EVM User's Guide prior to connecting any load to the EVM output. If there is uncertainty as to the load
specification, please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than 60°C. The EVM is designed to
operate properly with certain components above 105°C as long as the input and output ranges are maintained. These components
include but are not limited to linear regulators, switching transistors, pass transistors, and current sense resistors. These types of
devices can be identified using the EVM schematic located in the EVM User's Guide. When placing measurement probes near
these devices during operation, please be aware that these devices may be very warm to the touch.
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