BQ24074 PCB Design Guide: Footprint, Pinout, and Alternatives
Single-cell Li-Ion linear charger with dynamic power path, 1.5-A charge current, and 28-V tolerant input.
The BQ24074 is TI's standalone single-cell Li-Ion linear charger with dynamic power path management (DPPM), in a 3.00 mm × 3.00 mm VQFN-16. It charges the battery at up to 1.5 A while independently powering the system from a regulated 4.4-V OUT rail, so the load runs whenever a source is present — including instant-on with a fully discharged or absent battery. The input is USB-aware, with selectable USB100/USB500 current limits and a resistor-programmable limit up to 1.5 A, and this is the high-input-tolerance member of the BQ2407x family: 28-V absolute-maximum input with overvoltage protection at 10.5 V typical, versus 6.6 V for its siblings. Its other family distinction is a programmable termination current on the ITERM pin.
The reason to pick it over a cheap single-node charger is the power path: charge current and system load are metered separately, so charge termination and the safety timers keep working while the system runs, and the battery supplements the rail when the adapter runs out of current. The honest costs: it is linear, so the voltage dropped between IN and BAT at up to 1.5 A becomes heat in a 3-mm package and the thermal loop will quietly derate your charge rate; the 4.2-V battery target and 4.4-V system rail are fixed, not adjustable; and despite the 28-V rating it only operates up to 10.2 V in. If you need multi-amp charging, an adjustable battery voltage, or efficiency from a higher-voltage source, move up to a switching charger.
In the field, BQ24074 problems cluster into five board-level mistakes, covered below: expecting it to charge from an adapter above the OVP threshold because the pin is 28-V rated, ignoring linear dissipation until the thermal loop caps the charge current, leaving the TS pin floating so the part indicates charging while doing nothing, treating OUT as a stiff 5-V pass-through, and misreading the timer and termination interactions with DPPM as a defective part.
What breaks boards
28-V tolerant does not mean high-voltage operation: charging stops at the 10.5-V OVP
The IN pin survives −0.3 to 28 V absolute maximum, but the operating range is 4.35–10.2 V and the OVP comparator trips at 10.5 V typical — 10.2 V minimum, so some units trip right at the top of the operating range. Above OVP nothing is damaged, but the input FET turns off, PGOOD goes high-impedance, and OUT falls back to the battery. The 28-V rating exists to survive wrong adapters and hot-plug transients, not to run from them. Design around a 5-V source; a higher-voltage rail needs a switching charger instead.
It is a linear charger: the thermal loop, not RISET, often sets the real charge current
The voltage between IN and BAT times the charge current is dissipated in a 3-mm package with a junction-to-ambient thermal resistance of 44.5 C/W. When the die reaches TJ(REG) = 125 C the part silently folds back charge current; at 155 C it turns the input FET off entirely (20 C hysteresis, hiccup mode if it persists). The symptoms are a 1.5-A design that never draws 1.5 A and charge times that stretch, because the safety timers slow proportionally with the reduced current. Solder the thermal pad to real copper with vias — it is also the device's main ground connection.
A floating TS pin means no charging — while CHG still says charging
TS expects a 10-kOhm NTC (103AT-2, Vishay Type 2 curve) in the battery pack, giving 0 C and 50 C trip points with 3 C hysteresis. Outside that window the charger suspends, but the CHG pin stays low, so the status LED shows a healthy charge that never progresses. Bare cells without a pack thermistor are common in small builds; if you don't use the function, connect a 10-kOhm resistor from TS to VSS. Leaving TS floating or strapping it straight to ground both park the pin outside the valid window and stop charging.
OUT is a regulated 4.4-V rail, not a 5-V pass-through — and it sags by design
With an input present, OUT regulates at 4.4 V typical (4.3 minimum), less a dropout of 300 mV typical at 1 A when the input runs low. Budget downstream electronics for that, not for the adapter's 5 V. And 4.4 V is only the ceiling: when system load plus charge current exceeds the input current limit, the DPPM loop lets OUT droop to VO(REG) − 100 mV while it steals current back from the charger, and under further load the battery supplements the rail at VBAT − 40 mV — OUT is then essentially at battery voltage. Everything on OUT must work across the full battery range.
Timer faults and never-terminating charges usually trace to the power path, not a bad part
Termination detection is disabled whenever the DPPM, VIN-DPM, or thermal loop is reducing the charge rate — so a system that loads OUT during charging can legitimately never terminate. The default safety timers are 1800 s pre-charge and 18000 s fast charge (TMR floating); the timer clock slows proportionally with folded-back charge current, and when a timer finally expires, CHG flashes at approximately 2 Hz until CE or input power is toggled. Programming ICHG above the input current limit also stretches the timers, since charging runs at the slower input-limited rate. Size RTMR (18–72 kOhm) for the real, loaded charge rate.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Input voltage range (IN) | 4.35-10.2 V operating (BQ24074; '72/'73/'75/'79 grades: 4.35-6.4 V); IN voltage range 4.35-26 V; absolute maximum IN -0.3 to 28 V | SLUS810N Rev N, Section 8.3 Recommended Operating Conditions (IN rows) + Section 8.1 Absolute Maximum Ratings (IN with respect to VSS) |
| Input OVP threshold (VOVP) | 10.5 V typ (10.2 min / 10.8 max; VIN: 5 V -> 11 V) for BQ24074; family variants '72/'73/'75/'79 are 6.6 V typ | SLUS810N Rev N, Section 8.5 Electrical Characteristics, INPUT (VOVP row) + Section 6 Device Comparison Table |
| OUT pin voltage regulation (VO(REG)) | 4.4 V typ (4.3 min / 4.5 max; VIN > VOUT + VDO(IN-OUT); BQ24073, BQ24074 row) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, POWER PATH (VO(REG) rows) |
| Battery charge voltage (VBAT(REG)) | 4.20 V typ (4.16 min / 4.23 max; '72/'73/'74/'75) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, BATTERY CHARGER (VBAT(REG) row) |
| Battery fast charge current (ICHG) | Range 100 mA min to 1500 mA max (VBAT(REG) > VBAT > VLOWV, VIN = 5 V, CE = LO, EN1 = LO, EN2 = HI); ICHG = KISET/RISET with KISET = 890 AOhm typ (797 min / 975 max) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, BATTERY CHARGER (ICHG and KISET rows) |
| Input current limit (IINmax) | 95 mA typ (90 min / 100 max; EN1 = LO, EN2 = LO, USB100); 475 mA typ (450 min / 500 max; EN1 = HI, EN2 = LO, USB500); programmable 200-1500 mA (EN2 = HI, EN1 = LO, RILIM = 8 kOhm to 1.1 kOhm; KILIM = 1610 AOhm typ for ILIM = 500 mA to 1.5 A) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, POWER PATH (IINmax and KILIM rows) |
| Power-path dropout | VDO(IN-OUT) = 300 mV typ / 475 mV max (VIN = 4.3 V, IIN = 1 A, VBAT = 4.2 V); VDO(BAT-OUT) = 50 mV typ / 100 mV max (IOUT = 1 A, VIN = 0 V, VBAT > 3 V) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, POWER PATH (VDO(IN-OUT) and VDO(BAT-OUT) rows) |
| DPPM / battery supplement thresholds | VDPPM = VO(REG) - 100 mV typ ('72/'73/'74 row); battery supplement mode entered when VOUT falls to VBAT - 40 mV (VBSUP1) and exited when VOUT rises to VBAT - 20 mV (VBSUP2); battery termination is disabled while in DPPM mode or supplement mode, and termination detection is disabled whenever the charge rate is reduced by the thermal loop, the DPPM loop or the VIN-DPM loop | SLUS810N Rev N, Section 8.5 Electrical Characteristics, POWER PATH (VDPPM, VBSUP1, VBSUP2 rows) + Section 9.3.4.1.2 DPPM Mode + Section 9.3.4.1.3 Battery Supplement Mode + Section 9.3.5 Battery Charging |
| Charge termination current (ITERM) | Internally set default 0.1 x ICHG typ (0.09 min / 0.11 max; CE = LO, (EN1, EN2) not (LO, LO)) or 0.033 x ICHG typ ((EN1, EN2) = (LO, LO), USB100); externally programmable via RITERM up to 50% of the fastcharge current, RITERM must be less than 15 kOhm; leave ITERM unconnected to select the internal default | SLUS810N Rev N, Section 8.5 Electrical Characteristics, BATTERY CHARGER (ITERM rows) + Section 9.3.5.2 Adjustable Termination Threshold (ITERM Input, BQ24074) |
| Charge safety timers | tPRECHG = 1800 s typ (1440 min / 2160 max) and tMAXCHG = 18000 s typ (14400 min / 21600 max) with TMR floating; programmable with RTMR = 18-72 kOhm (tPRECHG = KTMR x RTMR, tMAXCHG = 10 x KTMR x RTMR, KTMR = 48 s/kOhm typ); connect TMR to VSS to disable the timers; CHG flashes at approximately 2 Hz on a timer fault | SLUS810N Rev N, Section 8.5 Electrical Characteristics, BATTERY CHARGING TIMERS (tPRECHG, tMAXCHG, KTMR rows) + Section 8.3 Recommended Operating Conditions (RTMR row) + Section 9.3.5.6 Dynamic Charge Timers (TMR Input) + Section 9.3.5.7 Status Indicators |
| TS battery-temperature input | Trip points of 0 C and 50 C while charging, with 3 C hysteresis, with a Vishay Type 2 curve NTC with an R25 of 10 kOhm (103AT-2); VHOT = 300 mV typ (270 min / 330 max; VTS falling), VCOLD = 2100 mV typ (2000 min / 2200 max; VTS rising), INTC bias = 75 uA typ (72 min / 78 max); charging is suspended while the voltage at TS is outside the window and the CHG pin remains low; connect a 10-kOhm resistor from TS to VSS if the function is not required | SLUS810N Rev N, Section 8.5 Electrical Characteristics, BATTERY-PACK NTC MONITOR (VHOT, VCOLD, INTC rows + footnote 1) + Section 9.3.6 Battery Pack Temperature Monitoring + Section 10.2.2.3 TS Function |
| Thermal regulation / shutdown | TJ(REG) = 125 C temperature regulation limit (charge current reduced); TJ(OFF) = 155 C thermal shutdown (TJ rising, input FET turned off) with 20 C hysteresis; junction-to-ambient thermal resistance 44.5 C/W (RGT, 16 pins) | SLUS810N Rev N, Section 8.5 Electrical Characteristics, THERMAL REGULATION (TJ(REG), TJ(OFF), TJ(OFF-HYS) rows) + Section 8.4 Thermal Information + Section 9.3.5.8 Thermal Regulation and Thermal Shutdown |
| Pin-strap defaults (ISET, ILIM, EN1/EN2, IN bypass) | Charging is disabled if ISET is left unconnected (connect a 590 Ohm to 8.9 kOhm resistor from ISET to VSS to program the fast charge current level); leaving ILIM unconnected disables all charging (connect a 1100 Ohm to 8 kOhm resistor from ILIM to VSS; the input current includes the system load and the battery charge current); EN1 and EN2 are internally pulled down with approximately 285 kOhm - do not leave EN1 or EN2 unconnected to ensure proper operation; connect a bypass capacitor of 1 uF to 10 uF from IN to VSS | SLUS810N Rev N, Section 7 Pin Functions (ISET, ILIM, EN1, EN2, IN rows) |
| OVP behavior | The BQ2407x accepts inputs up to 28 V without damage; the overvoltage protection circuit shuts off the internal LDO and discontinues charging when VIN > VOVP for longer than the OVP deglitch time; when in OVP, the system output (OUT) is connected to the battery and PGOOD is high impedance; once the OVP condition is removed a new power-on sequence starts, the safety timers are reset and a new charge cycle is indicated by the CHG output | SLUS810N Rev N, Section 9.3.3 Overvoltage Protection (OVP) |
| Thermal pad grounding | There is an internal electrical connection between the exposed thermal pad and the VSS pin of the device; the thermal pad must be connected to the same potential as the VSS pin on the printed circuit board; do not use the thermal pad as the primary ground input for the device - the VSS pin must be connected to ground at all times; the thermal pad is also the main ground connection for the device and must be soldered to the printed circuit board | SLUS810N Rev N, Section 7 Pin Functions (Thermal Pad note) + Section 12.1 Layout Guidelines + RGT mechanical drawing note 3 |
Verified against the manufacturer datasheet on 2026-07-10. Confirm the current revision before production use.
Alternatives
- BQ24075: same family and footprint; trades the '74's programmable termination current (ITERM) for a SYSOFF battery-disconnect input, with the family-standard 6.6-V OVP and a 5.5-V OUT rail instead of 10.5-V OVP / 4.4-V OUT. An automotive BQ24075-Q1 grade also exists.
- BQ24073: same family with the same 4.4-V OUT regulation, but 6.6-V OVP and a TD termination-disable pin in place of the programmable ITERM. The pick when you don't need the '74's high input tolerance.
- MCP73871: Microchip's load-sharing single-cell charger and the common non-TI substitute, but it tops out at 1 A charge current and has no 10.5-V-class input OVP rating.
Common questions
- Can the BQ24074 charge from an adapter above 10.2 V?
- No. The operating input range is 4.35–10.2 V and the OVP threshold is 10.5 V typical (10.2 V minimum); above it the part stops charging, turns off the input FET, and runs the system from the battery until the input returns to range. The pin itself tolerates 26 V (28 V absolute maximum), so a wrong adapter won't destroy the part — it just won't charge.
- How do I set the charge current on the BQ24074?
- With a resistor from ISET to VSS: ICHG = KISET/RISET, where KISET is 890 AOhm typical, over a usable fast-charge range of 100 mA to 1500 mA. The input current limit still gates the real rate: in USB100 or USB500 mode at most about 100 mA or 500 mA flows in, shared between the system load and the battery, and charging simply runs slower than the ISET value.
- Why is my BQ24074 not charging?
- Check TS first: it must see a valid thermistor voltage, and boards without a pack NTC need a 10-kOhm resistor from TS to VSS — otherwise the charger suspends while CHG still indicates charging. Then confirm CE is low (charge enable is active-low) and that EN1 and EN2 are not both high, which is USB-suspend/standby and disables the input path entirely.
- What does the OUT pin provide when no input is connected?
- OUT is powered from the battery through the internal battery FET with 50 mV typical dropout at 1 A, so it tracks battery voltage; the 4.4-V regulation applies only while a valid input is present. Current is not regulated in this mode, but the short-circuit protection on OUT stays active.