Renesas ISL9241 Installation and operating instructions

Application Note
R16AN0002EU0300 Rev.3.00 Page 1
Jan 6, 2022 © 2018 Renesas Electronics
Abstract
The ISL9241 is a Buck-Boost battery charger that supports Narrow Voltage Direct Charging (NVDC) and Hybrid
Power Buck-Boost (HPBB/Bypass) operation modes. It also has special features such as Supplemental mode
(Intel Vmin Active Protection), USB On-the-Go (OTG), and USB PD operation modes (by operating the charger in
reverse direction). All modes are configurable by firmware. This document explains how to configure the ISL9241
to operate and transition between the different modes through SMBus and I2C communication.
Contents
1. ISL9241 Operation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Narrow Voltage Direct Charging (NVDC) Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 NVDC Turbo Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Bypass Mode with Battery Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Reverse Turbo Boost (RTB) Mode with Battery Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Battery Only Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Supplemental Mode (Intel VAP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Transitioning Between Modes (NVDC/Bypass/RTB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Transitioning from NVDC or NVDC + CHRG to Bypass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Transitioning from Bypass to NVDC or NVDC + CHRG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Transitioning to Charging and Reverse Turbo Boost (RTB) States . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Adapter Removal Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5 Calculating Wait Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5.1 Calculating Time to Charge VSYS Node Before Turning on Bypass Gate . . . . . . . . . . . . . 14
2.5.2 Calculating Wait Time to Allow CSOP to Discharge to VBAT . . . . . . . . . . . . . . . . . . . . . . . 14
2.5.3 Calculating Time to Charge VSYS Node Before Turning on NGATE . . . . . . . . . . . . . . . . . 14
3. Transitioning to OTG Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Transitioning to Supplemental Mode (Intel VAP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1 Entering Supplemental Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Calculating Charge Current Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Discharging Input Capacitor Before Plugging in Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5. Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
ISL9241 Operation Modes

R16AN0002EU0300 Rev.3.00 Page 2
Jan 6, 2022
ISL9241 Operation Modes Application Note
1. ISL9241 Operation Modes
The ISL9241 buck-boost charger supports several operation modes depending on battery availability and power
requirements. The ISL9241 can switch between modes during system operation using only firmware. When a
battery is the only power source in the system, the ISL9241 operates in Battery Only mode, consuming very little
current and transferring power to the system with very high efficiency. When an adapter is plugged into the
system, the ISL9241 starts up initially in NVDC mode and can be set up for other modes through firmware from a
controller on the board.
ISL9241 Operation Modes:
▪NVDC mode (default): see Narrow Voltage Direct Charging (NVDC) Mode
▪Bypass mode with battery charging: see Bypass Mode with Battery Charging
▪Reverse Turbo mode with battery charging: see Reverse Turbo Boost (RTB) Mode with Battery Charging
▪Battery Only mode: see Battery Only Mode
▪Supplemental mode (Intel Vmin Active Protection (VAP)): see Supplemental Mode (Intel VAP)
1.1 Narrow Voltage Direct Charging (NVDC) Mode
In Narrow Voltage Direct Charging (NVDC) mode, the power from the adapter provides power to the system loads
and for battery charging. All power from the adapter passes through the power stage and the inductor. The
advantage of NVDC mode is that the system voltage can be regulated near the battery voltage. This allows you to
select lower voltage components for all the voltage regulators connected at the output system node, resulting in
smaller size and higher efficiency in the subsequent stages. This mode is more suitable for lower power operation
and for operation in Boost mode and Buck-Boost mode.
.
Figure 1. NVDC Operation Mode
When the system power increases, the available adapter power provides power to the system first. Any remaining
power is used to charge the battery.
InputPower
SystemPower
Battery
ChargePower
BatteryDischarge
PowerorTurbo
ModePower
SwitchisON

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Jan 6, 2022
ISL9241 Operation Modes Application Note
1.1.1 NVDC Turbo Mode
When the system power exceeds the power that can be provided by the adapter, the ISL9241 regulates the
adapter current at the Adapter Current Limit value. The remaining power to the system is provided from the
battery, so the adapter and the battery provide the system power together. This is called NVDC Turbo mode.
1.2 Bypass Mode with Battery Charging
When the adapter voltage is higher than the battery voltage, the ISL9241 can be operated in Bypass mode. In
Bypass mode, the adapter is connected directly to the system and the system power is provided directly from the
adapter. The charging and discharging power goes through the power stage and inductor.
When the available adapter power is higher than the power consumed by the system, the remaining power is used
to charge the battery. When the battery is not charging, the converter is not switching. When charging starts, the
converter starts switching in the forward direction, delivering power from the adapter to charge the battery.
Figure 2. Bypass Mode with Battery Charging
Input Power
System Power
Battery
Charge Power
Switch is OFF, but diode path
supports power from the
battery (VADP > VBAT to use
Bypass mode)

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Jan 6, 2022
ISL9241 Operation Modes Application Note
1.3 Reverse Turbo Boost (RTB) Mode with Battery Charging
If the ISL9241 is configured to operate in Bypass mode, Reverse Turbo Boost (RTB) mode can be enabled. RTB
mode is useful when the adapter alone cannot handle the peak power demands from the system. In RTB mode,
the battery supplements the adapter power by operating the ISL9241 in the reverse direction.
Initially, when the system load is lower than the adapter power, all the system power is provided from the adapter.
As the system load increases, the ISL9241 provides power from the adapter up to the programmed Adapter
Current Limit. When the Adapter Current Limit is reached, the ISL9241 operates in the reverse direction, boosting
up the power from the battery and providing the remaining needed power in addition to the adapter power. The
ISL9241 can go from forward battery charging to RTB mode automatically depending on the load demand. When
RTB mode is enabled, the battery FET (connected to BGATE) is always turned on.
Figure 3. Reverse Turbo Boost with Battery Charging
Input Power
System Power
Reverse Turbo
Power Mode
Switch is OFF, but
diode path
supports discharge
from the battery
(VADP > VBAT to
use Bypass mode)

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Jan 6, 2022
ISL9241 Operation Modes Application Note
1.4 Battery Only Mode
When no adapter is present in the system, the ISL9241 provides all system load demands directly from the
battery. In this case, the system power passes only through the Battery FET and the FET connected to NGATE, so
the efficiency in Battery Only mode is very high. Because the control loop and several features are not needed in
Battery Only mode, these features can be turned off and the ISL9241 can operate in a low power state,
consuming very little current for operation.
When the ISL9241 is operating in Battery Only mode, you can connect a battery-powered device to the USB port
(adapter side). The ISL9241 can support battery-powered devices by operating in the reverse direction and
providing power from the battery to the adapter terminal/USB port. This is called On-the-Go (OTG) mode, but
supports USB-OTG and USB-PD. The ISL9241 can operate in Reverse Buck/Boost mode or Buck-Boost mode
and provides a programmable 5V to 20V output at the USB port.
Figure 4. Battery Only Mode and OTG Mode
OTGPower
SystemPower
BatteryMode
Power
SwitchisON

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Jan 6, 2022
ISL9241 Operation Modes Application Note
1.5 Supplemental Mode (Intel VAP)
Use Supplemental mode or Intel VMIN Active Protection (VAP) when the battery voltage is sufficient to provide
power to the system but the impedance from the battery to the system causes a large voltage drop, limiting the
power that can be drawn without crashing the system. This mode also supports rare peak power events that are
higher than what the battery power can support. Use this mode when there is only a battery in the system and the
adapter port is open.
When the battery voltage is high, the ISL9241 operates in reverse direction (OTG mode) and stores some energy
from the battery in the input capacitors (on the adapter side) at high voltage.
If the system voltage starts falling below a threshold during a high system load event due to high battery
impedance or low battery voltage, the energy from the input capacitor supplements the battery power and holds
up the system voltage until the load event ends.
After receiving the command to exit the mode, the energy stored in the input capacitors can be discharged using
an internal discharge path so that an external power source can be safely connected.
This mode’s setup can be controlled by an external microcontroller or host controller on the system. Several
parameters can be programmed to achieve the needed response from the ISL9241.
Figure 5. Supplemental Mode (Intel VMIN Active Protection)
SystemPower
BatteryMode
Power
SwitchisON
OTGfor
StoredPower
StoredPower
onCapacitor

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Jan 6, 2022
ISL9241 Operation Modes Application Note
2. Transitioning Between Modes (NVDC/Bypass/RTB)
You can use firmware commands to configure the ISL9241 to transition between the different modes. Figure 6
shows the major and minor states that the ISL9241 can operate in and the transitions between them. The
commands in this document are suggestions/recommendations. You can start with these commands for your first
implementation/evaluation, but you must test the commands on your system to see if the commands need to be
modified for your application in your final implementation.
Bypass State: Set up the system with the Bypass gates ON to make VSYS = VADP and allow flow of current from
the adapter directly to the load. In this state, the adapter is connected directly to the system, but the ISL9241 is not
switching, so the charging and reverse turbo boost functions are disabled.
(BYPSG = on, NGATE = off, BGATE = off, MaxSysV = 0, RTB bit = 0, CC = 0, MinSysV= 0)
Bypass + Charging State: The adapter is connected directly to the system (Bypass) and charging is enabled, but
the turbo boost function is disabled. Use this state when the adapter can support the entire system load.
(BYPSG = on, NGATE = off, BGATE = on, MaxsysV = non-zero, RTB bit = 0, CC = non-zero, MinsysV = non-zero)
Reverse Turbo-Boost State (RTB): The Bypass gates are ON and Reverse Turbo Boost is enabled and primed
to meet any load requirements. The battery can supplement the adapter to provide power in this mode. Charging
is disabled.
(BYPSG = on, NGATE = off, BGATE = on, MaxsysV = non-zero, RTB bit = 1, CC = 0, MinsysV = 0)
RTB + Charging State: An extension of RTB with battery charging enabled.
(BYPSG = on, NGATE = off, BGATE = on, MaxsysV = non-zero, RTB bit = 1, CC = non-zero, MinsysV = non-zero)
Bat State: Reached when the adapter is unplugged and ACOK goes low. The system load is supported by the
battery.
(BYPSG = off, NGATE = on, BGATE = on, MaxsysV = non-zero, RTB bit = 0, CC = 0, MinsysV = 0)
Figure 6. Transition State Diagram
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only if VBAT > MinSysVoltage

R16AN0002EU0300 Rev.3.00 Page 8
Jan 6, 2022
ISL9241 Operation Modes Application Note
2.1 Transitioning from NVDC or NVDC + CHRG to Bypass
Note: To transition from NVDC mode to Bypass mode, turn off charging first. The system load must be reduced so
that the ISL9241 input current never exceeds the Adapter Current Limit, ensuring smooth transition.
The output voltage of the ISL9241 is raised to the adapter voltage and the Bypass FETs are closed. When the
system is connected to the adapter, NGATE is turned off to isolate the system from the output of the ISL9241. The
ISL9241 output is then ramped down close to the battery voltage so that charging can be enabled safely any time.
The steps in Table 1 ensure that the transition and subsequent operation are smooth. You can skip any of the
recommended steps (in yellow) if you test and verify that your system works smoothly and without any glitches
without the step.
Table 1. Transitioning from NVDC (or NVDC + CHRG) Mode to Bypass Mode
Step
Number Function Description Register Name Value (Decimal)
Read/
Write
Register
Address
LNVDC + CHRG to NVDC
1 Set Charge current register to 0 to disable fast
charging
ChargeCurrentLimit 0 Write 0x14
2 Set MinSysVoltage register to 0 to disable
trickle charging
MinSysVoltage 0 Write 0x3E
ANVDC to Bypass
Preparation Set adapter current limit to appropriate value ACLIM Adapter specific Write 0x3F
Preparation Reduce system load below ACLIM
Preparation Enable ADC (to read ADC values) if using it
after Step2
Control 3 <0> 1 Write 0x4C
1 Turn on the VIN/VOUT comparator so the
Bypass gate turns off when the adapter is
removed
Control 0<5> 1 Write 0x39
2 Set MaxsysV = VADP (from ADC or PD
controller) - 2V
For 20V adapter, set 18.304V
Vin ADC Read 0x87
MaxSysVoltage
register
Vin ADC
register - 2V
Write 0x15
Three options:
▪Wait fixed time (see Calculating Wait Time to
calculate wait time)
▪Wait fixed time and read ADC to confirm
VSYS = MaxsysV register
▪Poll ADC and check when VSYS = MaxsysV
register
3 Set ACOK reference to (800mV + ADC
tolerance) higher than the battery full charge
voltage (so the charger can detect and let the
input ramp down during adapter removal
events) and also Vin_ADC - 3V to account for
ADC tolerance and I*R drop
ACOKREF Vin_min - I*R
drop (~2V) >
ACOKREF >
VBAT+1.1V
Write 0x40
4 Turn on Bypass gate, turn off NGATE, set
Charge pumps to 100% and Enable 10mA
current source
Control 0 Hex 3860 Write 0x39
5 Stop switching after 1ms (Wait time for Bypass
FET to turn on)
MaxsysV register 0 Write 0x15
6 Disable 10mA discharge on CSOP Control 0 Hex 1860 Write 0x39
7 Force Forward Buck/ Reverse Boost mode Control 4<10> 1 Write 0x4E

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Jan 6, 2022
ISL9241 Operation Modes Application Note
Suggestions:
▪If the adapter is removed at any time and ACOK goes low during Steps 1 to 3, stop executing the commands
and complete steps for Bypass to BAT state.
▪If the adapter is removed after Step 4, complete all steps and then execute the commands for Bypass to BAT.
▪If the adapter is removed after completing all steps, first transition to Bypass state (from Bypass+Charging or
Reverse Turbo Boost) and then transition to BAT state.
▪CV mode regulation is not recommended in Bypass mode without Charging or Reverse Turbo boost. So enable
charging and Reverse Turbo Boost along with setting MaxsysV to non-zero value.
▪NGATE FET and Bypass FET power good signals can be read from the Information 1 register (0x3A) to ensure
that there is no unexpected behavior in the system.
▪Enable slew rate if output caps are high and inrush can be high to prevent protection from tripping. Capacitor
can be added on Bypass gate if inrush during turn on needs to be limited.
2.2 Transitioning from Bypass to NVDC or NVDC + CHRG
Note: To transition from Bypass mode to NVDC, turn off charging and RTB mode first. The system load must be
reduced so that the system current never exceeds the ISL9241 Adapter Current Limit value.
After turning off the battery FET, the ISL9241 output is ramped up to the adapter voltage. The NGATE FET is
closed, connecting the output of the ISL9241 to the system. The Bypass FETs then open, isolating the adapter
and the system output. The ISL9241 output and system are ramped down close to the battery voltage so that
charging can be enabled safely any time. The system is regulated close to the battery voltage at the value
programmed in the MaxSystemVoltage register. Complete the steps in Tabl e 2 to transition from Bypass mode to
NVDC mode or NVDC + Charge mode.
Table 2. Transitioning from Bypass Mode to NVDC (or NVDC + CHRG) Mode
Step
Number Function Description Register Name
Value
(Decimal) Read/ Write
Register
Address
BBypass to NVDC
Preparatio
n
Reduce system load below ACLIM
1 Disable Force Forward Buck/ Reverse Boost
mode
Control 4<10> 0 Write 0x4E
2 Turn off VIN/VOUT comparator Control 0<5> 0 Write 0x39
3 Set MaxSysVoltage = VADP (from ADC or
PD controller) - 2V
For 20V adapter, set 18.304V
Vin ADC register Read 0x87
MaxSysVoltage
register
Vin ADC
register - 2V
Write 0x15
Three options:
▪Wait fixed time (see Calculating Wait Time
to calculate wait time)
▪Wait fixed time and read ADC to confirm
VSYS = MaxSysVoltage register
▪Poll ADC and check when
VSYS = MaxsysV register
4 Turn off Bypass gate, turn on NGATE, set
charge pumps to 100%, Enable 10mA
current source
Control 0 Hex 2040 Write 0x39
5 Set MaxSysVoltage = Battery full charge
voltage after 1ms
MaxSysVoltage
register
Battery specific Write 0x15

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Jan 6, 2022
ISL9241 Operation Modes Application Note
2.3 Transitioning to Charging and Reverse Turbo Boost (RTB) States
When the ISL9241 has transitioned completely into Bypass mode (or NVDC mode), enable the charging and/or
Reverse Turbo Boost (RTB) modes using the commands in Table 3.
6 Disable 10mA discharge on CSOP after
10ms (or until CSOP ramps down to
MaxsysV), set charge pumps to 2%
Control 0 Hex 0000 Write 0x39
KNVDC to
NVDC + CHRG
1 Set MinSysVoltage to non-zero value to
enable trickle charging
MinSysVoltage Battery specific Write 0x3E
2 Set charge current limit to non-zero value to
allow charging
ChargeCurrentLimi
t
Battery specific Write 0x14
Table 3. Transitioning Between Bypass Mode and Charging and Reverse Turbo Boost States
Transition From State To State
Step
Number Function Description Register Name
Value
(Decimal)
Register
Address
CBypassRTB
(Reverse
Turbo Boost)
1 Reduce system load
below ACLIM
2 Enable Reverse Turbo
Boost function
Control 0<0> 1 0x39
3 Set MaxSysVoltage
register to full battery
charge voltage
MaxSysVoltage Battery
specific
0x15
DRTBRTB+
CHRG
1 Set MinSysVoltage to
non-zero value to enable
trickle charging
MinSysVoltage Battery
specific
0x3E
2 Set charge current limit to
non-zero value to allow
charging
ChargeCurrentLimit Battery
specific
0x14
ERTB+
CHRG
RTB 1 Disable fast charging ChargeCurrentLimit 0 0x14
2 Disable trickle charging MinSysVoltage 0 0x3E
F RTB Bypass 1 Reduce system load
below ACLIM
2 Disable switching MaxSysVoltage 0 0x15
3 Disable reverse turbo
boost function
Control 0<0> 0 0x39
Table 2. Transitioning from Bypass Mode to NVDC (or NVDC + CHRG) Mode (Cont.)
Step
Number Function Description Register Name
Value
(Decimal) Read/ Write
Register
Address