CHARGER — Battery charger

The battery charger is suitable for any general purpose applications with lithium-ion/lithium-polymer battery types.

The main features of the battery charger are the following:

Charging cycle

Battery charging starts after a VBUS connection and the battery is detected.

If a battery is found, trickle charging begins. Fast charging starts when the battery voltage is above VTRICKLE_FAST. After the battery voltage reaches VTERM, the charger enters constant voltage charging. The battery voltage is maintained while monitoring current flow into the battery. When the current into the battery drops below ITERM, charging is complete. The charger waits until the battery voltage is below VRECHARGE before starting a new charging cycle.

To charge the battery, VBUS voltage must be higher than VBAT voltage during the charge cycle. This means VBUS must be VBUS(V) > VBAT(V) + VDROPOUT_VBUS. If this condition is not met the charge cycle stops.

Figure 1. Charging cycle flow chart
Flow chart of charging cycle
Figure 2. Charging cycle
Charging cycle

Termination voltage (VTERMSET)

The termination voltage, VTERM, is set using VTERMSET to support two values of battery charging termination voltage for the chosen product option.

Product option VTERMSET VTERM threshold
Standard VTERM LOW 4.1 V
Standard VTERM HIGH 4.2 V
High VTERM LOW 4.25 V
High VTERM HIGH 4.35 V

Termination and trickle charge current

Termination current and trickle charge current are set to a percentage of the charge current limit (ICHGLIM).

See Electrical specification for the limits.

Charge current limit (ICHG)

The charge current limit is set between 20 mA and 400 mA by connecting the RICHG resistor to the ICHG and AVSS pins.

The following equation gives the resistance to be connected based on the ICHGLIM.

The following apply when the RICHG resistor is between 0 Ω and 30 kΩ.
  • ICHGLIM is the fast charge current limit in Amps
  • RICHG is the resistance to be connected between the ICHG and AVSS pins in Ω

Common values are provided in the following table.

Table 2. Common charge current values
RICHG resistor value Nominal charge current limit, ICHGLIM Error
0 (short to AVSS) 400 mA ± ICHGACC%
1.5 kΩ 200 mA ± (ICHGACC + RICHGACC)%
4.7 kΩ 100 mA ± (ICHGACC + RICHGACC)%
11 kΩ 50 mA ± (ICHGACC + RICHGACC)%
30 kΩ 20 mA ± (ICHGACC + RICHGACC)%
Note: ICHGLIM must be set at or below the safe charge current limit of the battery according to the battery specification.

Battery thermal protection using NTC thermistor (NTC)

Battery thermal protection is implemented in the following two ways.

  • Using a battery pack with an integrated NTC thermistor
  • Connecting a thermistor between the NTC pin and the AVSS pin
The thermistor needs to have thermal contact with the battery and preferably within the battery pack. Recommended values for the NTC thermistor are found in the following table.
Table 3. Recommended NTC thermistor values
Parameter Value Unit
Nominal resistance at 25°C 10 kΩ
Resistance accuracy 1 %
B25/50 constant 3380 Kelvin
B25/85 constant 3434 to 3435 Kelvin
B constant accuracy 1 %

If the thermal protection feature is not used, then a 10 kΩ, ≤20% accuracy resistor should be connected between NTC and AVSS pins.

To provide JEITA compliant thermal protection, the charge current limit and termination voltage are adjusted according to the NTC thermistor measurement.

Table 4. Battery temperature ranges
Temperature region Battery temperature Charging current Termination voltage
Cold T < 0°C 0 (OFF) NA
Cool 0°C < T < 10°C IREDUCED VTERM
Nominal 10°C < T < 45°C ICHGLIM VTERM
Hot T > 60°C 0 (OFF) NA

Charger thermal regulation

If the device junction temperature exceeds THIGH and CHARGER is in Fast Charge mode, the charge current is reduced to IREDUCED.

Charger error conditions

A CHARGER error condition occurs when one of the following are present:

  • A battery short (VBAT to AVSS)
  • Battery voltage lower than VBATCHARGEMIN after battery detection due to a fault with the battery
  • Trickle charge timeout; see TOUTTRICKLE
  • Constant voltage charge/fast charge timeout; see TOUTCHARGE
  • Device internal error occurs when CHARGER is self-checking

After an error is detected, CHARGER is disabled, the charging error indication is activated, and the charging indication is deactivated. Error conditions are cleared when VBUS is disconnected and reconnected again.

Note: The constant voltage/fast charge timeout is the combined time spent in both constant voltage charge and fast charge, TOUTCHARGE.

Charging indication (CHG) and charging error indication (ERR)

The charging indication pin CHG and charging error indication pin ERR sink 5 mA of current when active. They are high impedance when disabled. This is suitable for driving LEDs or connecting to host GPIOs in a weak pull-up configuration.

Figure 3. Configuration for connecting to LEDs
Figure 4. Configuration for connecting to a host
Note: To configure both LED indication and connection to a host, the GPIO input voltage range tolerance must be met, or an external circuit may be required. See Reference circuitry.

The charging indication pin, CHG, is active while the battery is charging.

The charging error indication pin, ERR, is activated when an error occurs, see Charger error conditions.

DPPM — Dynamic power-path management

CHARGER manages battery current flow to maintain VINT voltage.

The system load requirements are prioritized over battery charge current when VBUS is connected and the battery is charging. The battery is isolated when VBUS is connected and the battery is fully charged. SYSREG supplies the load unless the load exceeds SYSREG limits. When VBUS is disconnected, CHARGER switches to battery supply.

During charging, if the combined current load ILOAD on VINT (including BUCK input current) and VBAT (ICHG) exceeds the current provided by SYSREG (ILIM), the battery charge current decreases to maintain the VINT voltage. The battery charger reduces the current to maintain the internal voltage: VINT = V(VBAT )+ VDROPOUT_CHARGER. If more current is required, CHARGER enters Supplement mode, switching to provide current from the battery, up to IBATLIM.

If a charge cycle ends and ILOAD exceeds ILIM, CHARGER connects the battery and enters Supplement mode to maintain VINT.

When VBUS and the battery are connected, the maximum supported load is ILIM + IBATLIM.

When VBUS is disconnected, CHARGER sources current for VINT from the battery. In Supplement mode, or when VBUS is disconnected, VINT voltage is the same as the battery voltage.
Table 5. Battery supply
VBUS connected Battery connected Load CHARGER VINT supply VINT voltage
Yes Yes




(ICHG reduced)

Yes Yes ILOAD > ILIM Supplement mode VBUS and VBAT V(VBAT)1

1CHARGER has a resistance of RONCHARGER between VBAT and VINT. The voltage drop from VBAT to VINT is IBAT x RONCHARGER, where IBAT is the current being drawn from the battery.

Electrical specification

Table 6. CHARGER electrical specification
Symbol Description Min. Typ. Max. Unit
ICHGACC Fast Charge current accuracy for ICHG ≥ 50 mA, 0.1% accuracy external resistor   ±10   %
ICHGACC Fast Charge current accuracy for ICHG < 50 mA, 0.1% accuracy external resistor   ±15   %
VTERM0 Standard termination voltage, VTERMSET = LOW - 4.1 - V
VTERM1 Standard termination voltage, VTERMSET = HIGH - 4.2 - V
VTERM0 High termination voltage, VTERMSET = LOW - 4.25 - V
VTERM1 High termination voltage, VTERMSET = HIGH - 4.35 - V

Termination voltage accuracy

-1 - +1 %
VTHIGH_DELTA VTERM voltage reduction at high temperature   100   mV
ITERM Termination current 8 10 12 % of ICHG
ITRICKLE Trickle charge current   10   % of ICHG
IREDUCED Fast charge current when device junction temperature is above THIGH or battery temperature is below TNTCCOOL - 50 - % of ICHG
THIGH High temperature threshold - 100 - °C
THIGHHYST High temperature hysteresis - 10 - °C
VTRICKLE_FAST Trickle to Fast Charge threshold - 2.9 - V
VRECHARGE Recharge threshold - 97 - % of VTERM
VBATCHARGEMIN Minimum voltage during charge - 2.1 - V
TOUTTRICKLE Trickle charging timeout - 10 - min
TOUTCHARGE Timeout for Fast charging and constant current charging - 7 - hour
VDROPOUT_CHARGER VINT - VBAT voltage for charging - 50 - mV
VDROPOUT_VBUS Minimum VBUS - VBAT voltage for charging - 140 - mV
TREDETECT Period between detection events - 500 - ms
IBATLIM Output current limit from battery in discharge - 660 - mA
RONCHARGER CHARGER resistance between VBAT and VINT in Discharge, VBAT = 3.7 V - 130 230 mΩ
VBATPOR Power-on reset release voltage for VBAT - 2.7 - V
VBATBOR Brownout reset trigger voltage for VBAT 1 - 2.5 - V
ISINK DC current (CHG and ERR) - 5 - mA
TNTCCOLD JEITA cold temperature threshold (Thermistor: 10 kΩ, B25/50=3380 K) - 0 - °C
RNTCCOLD_FALLING Resistance threshold from cool to cold 25.53 27.28 29.13 kΩ
RNTCCOLD_RISING Resistance threshold from cold to cool 23.10 26.00 28.20 kΩ
TNTCCOOL JEITA cool temperature threshold (Thermistor: 10 kΩ, B25/50=3380 K) - 10 - °C
RNTCCOOL_FALLING Resistance threshold from nom. to cool 16.80 18.00 19.20 kΩ
RNTCCOOL_RISING Resistance threshold from cool to nom. 15.50 17.10 18.60 kΩ
TNTCWARM JEITA warm temperature threshold (Thermistor: 10 kΩ, B25/50=3380 K) - 45 - °C
RNTCWARM_FALLING Resistance threshold from warm to nom. 4.86 5.13 5.43 kΩ
RNTCWARM_RISING Resistance threshold from nom. to warm 4.68 4.92 5.17 kΩ
TNTCHOT JEITA hot temperature threshold (Thermistor: 10 kΩ, B25/50=3380 K) - 60 - °C
RNTCHOT_FALLING Resistance threshold from hot to warm 3.04 3.19 3.35 kΩ
RNTCHOT_RISING Resistance threshold from warm to hot 2.90 3.02 3.15 kΩ

1Device enters BOR only if (V(VBUS) < VBUSBOR) AND (V(VBAT) < VBATBOR).

Electrical characteristics

The following graphs show CHARGER electrical characteristics.

Figure 5. CHARGER RDS(ON) vs. VBAT voltage
Figure 6. Quiescent VBAT current vs. VBAT voltage
Quiescent VBAT current vs. VBAT voltage
Figure 7. CHARGER RDS(ON) vs. temperature
CHARGER RDS(ON) vs. temperature
Figure 8. Quiescent VBAT current vs. temperature
Quiescent VBAT current vs. temperature
Figure 9. VTERM vs. temperature
VTERM vs. temperature
Figure 10. Charge profile with ISET=1
Charge profile