RICHTEK RT4823M Wide Input and Ultra Low Quiescent Current Boost Converter with High Efficiency User Manual

User Manual for RICHTEK models including: RT4823M, Wide Input and Ultra Low Quiescent Current Boost Converter with High Efficiency, RT4823M Wide Input and Ultra Low Quiescent Current Boost Converter with High Efficiency, RT4823M Wide Input and Ultra Low Quiescent Current Boost Converter, Wide Input and Ultra Low Quiescent Current Boost Converter, Ultra Low Quiescent Current Boost Converter, Quiescent Current Boost Converter, Current Boost Converter, Boost Converter, Converter

Wide Input and Ultra-Low Quiescent Current Boost Converter with High Efficiency

NFC Device Power Supply, NFC Device Power Supply, USB Charging Ports, PC Accessory Application (Keyboard, Mouse...etc.), TWS (True Wireless Stereo) Hall Sensor, Gaming Device Sensor, Ultra-Low Operating Quiescent Current, Ultra-Low Operating Quiescent Current, Quickly Start-Up Time (< 400μsec), 3 Few External Components : 1μH Inductor, 0402 Case Size Input and 0603, Case Size Output Case Size Capacitors, Input Voltage Range : 1.8V to 5.5V, Support VIN > VOUT Operation, Boost Output Voltage Setting :

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DS4823M-00

RT4823M

Wide Input and Ultra-Low Quiescent Current Boost Converter with High Efficiency

General Description
The RT4823M allows systems to take advantage of new battery chemistries that can supply significant energy when the battery voltage is lower than the required voltage for system power ICs. By combining built-in power transistors, synchronous rectification, and low supply current; this IC provides a compact solution for systems using advanced Li-Ion battery chemistries.
The RT4823M is a boost regulator designed to provide a minimum output voltage from a single-cell Li-Ion battery, even when the battery voltage is below system minimum. In boost mode, output voltage regulation is guaranteed to a maximum load current of 1500mA. Quiescent current in shutdown mode is less than 1A, which maximizes battery life. The regulator transitions smoothly between bypass and normal boost mode. The device can be forced into bypass mode to reduce quiescent current.
The RT4823M is available in the WL-CSP-9B 1.3x1.2 (BSC) package.
Applications
NFC Device Power Supply USB Charging Ports PC Accessory Application (Keyboard, Mouse...etc.) TWS (True Wireless Stereo) Hall Sensor Gaming Device Sensor

Features
Ultra-Low Operating Quiescent Current Quickly Start-Up Time (< 400sec) 3 Few External Components : 1H Inductor, 0402
Case Size Input and 0603 Case Size Output Case Size Capacitors Input Voltage Range : 1.8V to 5.5V Support VIN > VOUT Operation Default Boost Output Voltage Setting : VOUT = 5V Maximum Continuous Load Current : 1.5A at VIN > 3V Boosting VOUT to 5V Up to 93% Efficiency EN(H), FPWM(H) : Forced PWM Mode EN(H) : Boost Mode EN(L) : Shutdown Mode Internal Synchronous Rectifier Over-Current Protection Cycle-by-Cycle Current Limit Over-Voltage Protection Short-Circuit Protection Over-Temperature Protection Small WL-CSP-9B 1.3x1.2 (BSC) Package

Simplified Application Circuit

RT4823M L

VOUT

COUT

VIN

CIN

FPWM GND

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RT4823M

Ordering Information

RT4823M

Package Type WSC : WL-CSP-9B 1.3x1.2 (BSC)

Pin Configuration
(TOP VIEW)

VOUT

Note : Richtek products are :
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.

VOUT A1 A2 A3 VIN
SW B1 B2 B3 EN SW
GND C1 C2 C3 FPWM

GND

Marking Information

9UW

9U : Product Code W : Date Code

WL-CSP-9B 1.3x1.2 (BSC)

Functional Pin Description

Pin No.

Pin Name

Pin Function

A1, A2 VOUT

Output voltage. Place COUT as close as possible to device.

VIN

Input voltage. This pin has to connect to input power, it's used to supply chip internal power.

B1, B2 SW

Switching node. The power inductor should be connected between SW and power input.

Enable. When this pin is set to HIGH, the circuit is enabled. Do not let this pin floating.

C1, C2 GND

Ground. This is power and signal ground reference for the chip. The COUT bypass capacitor should be returned with the shortest path possible to these pins.

FPWM

Force PWM mode. This pin is used to control converter into force PWM mode. When this pin is set to HIGH, the circuit is into FPWM mode. Do not let this pin floating.

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Functional Block Diagram
SW VIN
GND

RT4823M

Peak Current Sense

Valley Current Sense

RFB1 aFB

RFB2

sDis_chg

VOUT

EN FPWM

Driver

PWM Control Logic C2

gm-
+ VREF R1
C1

Soft-Start Control Logic

VINH
sDis_chg FAULT
OTP OVP SCP OCP

SWELL

VIN VOUT

Operation
The RT4823M combined built-in power transistors, synchronous rectification, and low supply current, it provides a compact solution for system using advanced Li-Ion battery chemistries. In boost mode, output voltage regulation is guaranteed to maximum load current of 1.5A. Quiescent current in Shutdown mode is less than 1A, which maximizes battery life.
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Power-On Reset
If input voltage is lower than POR, the internal digital and analog circuit is disable. If input voltage is higher than POR the Boost converter behavior is shown as follow : 1. IC Digital circuit will be activated. 2. Internal register will be load in default value. 3. Boost converter will into run free-running mode
(detail in free-running mode section).
4. If VOUT > 2.2V (or VIN > 2.2V), Boost converter will into close loop control and load in E-fuse value to internal register.
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RT4823M
Free-Running Mode
If both voltage of VIN and VOUT are lower than 2.2V, the Boost converter will into free-running mode. In this mode, switching frequency operation is 1.5MHz and duty cycle of Boost converter is 25%. It is translation of power-on stage, and there is implemented current limit function for converter soft-start. The current limit level should be lower than 900mA.

EN and FPWM
In the Table 1 shown, there are three device states in the RT4823M. When EN and FPWM pull low, it is into shutdown mode and quiescent current is less than 1A. If EN pull high, the RT4823M is into boost mode and it is with low quiescent operation. When the RT4823M is in the boost mode and pull high FPWM, the RT4823M is into FPWM mode. There should be a delay time (< 250s) from EN pull high to power ready to guarantee normal operation.

EN Input 0
1 1

FPWM Input 0
0 1

Table 1. Pin Configuration for Converter

Mode Define

Device State

Shutdown mode

The device is shutdown. The device shutdown current is approximately about 1A (max).

Boost PFM

The device is active in Boost PFM low quiescent mode. The supply current is approximately about 4A (typ.).

Boost PWM The device is into force PWM mode.

Enable
The boost can be enabled or disabled by the EN pin. When the EN pin is higher than the threshold of logic-high, the device starts operating follow Figure 1 operation diagram. In shutdown mode, the converter stops switching, internal control circuit is turned off. The output voltage is discharging by component consumption (Cap ESR...) that state have not discharge function.
Soft-Start State
During soft-start state, if VOUT reach to 99% VOUT_Target. The RT4823M will into boost operation. When system power-on with heavy loading (higher than pre-charge current), the RT4823M is in pre-charge state until loading release.
Boost/Auto Bypass Mode
EN = H There are two normal operation modes, one is the boost mode, and the other one is auto bypass mode. In the boost mode (VIN 0.3V < VOUT_Target), the converter boost output voltage to VOUT_Target, it delivers power to loading by internal synchronous switches after the soft-start state. In the auto bypass mode (VIN 0.3V VOUT_Target), input voltage will
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deliver and through to the output terminal loading directly. That can provide max current capacity with the RT4823M. Detail information is shown as below. Boost Mode (Auto PFM/PWM Control Method) In order to save power and improve efficiency at low loads, the Boost operate in PFM (Pulse Frequency Modulation) as the inductor drops into DCM (Discontinuous Current Mode). The switching frequency is proportional to loading to reach output voltage regulation. When loading is increase and inductor current is into continuous current mode, the Boost automatically gets in PWM mode.
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Mode LIN
Soft-Start Boost
Auto Bypass
VOUT
VOUT_Target 0.99 x VOUT_Target
VIN VIN - 200mV

RT4823M

Table 2. The RT4823M Start-Up Description

Description

Condition

Linear startup

VIN - 200mV VOUT

Boost soft-start

0.99 x VOUT_Target > VOUT VIN - 200mV

Boost mode

VOUT_Target 0.99 x VOUT_Target

If VIN increase higher than VOUT

Auto bypass mode

VIN VOUT Control loop auto transfer between auto bypass mode and boost mode.

Control loop auto transfer between bypass mode and boost mode

Linear Startup

Soft-Start

Boost mode

Auto bypass mode

Figure 1. VOUT Mode Transition Diagram with EN L to H and VIN Variation (IOUT = 0A)

Protection The RT4823M features some protections are listed in below table. It is described the protection behavior.

Protection Type
OCP_IL5A OCP OVP SCP
OTP
SCP_SS

Fault Event Trigger
IL_peak > 5A
IL_peak > 3.6A VOUT > 6V
VOUT < 0.7V

Fault Deglitch Time
No delay
No delay 100ns
No delay

Protection Method
Turn off UG, LG Stop LG switching
Turn off UG, LG Turn off UG, LG

Fault Protection Latch Time
20ms, Auto-recovery
N/A
N/A
20ms, Auto-recovery

Reset Method
IL_peak < 5A IL_valley < 3.3A
VOUT < 6V VOUT > 0.7V

TEMP > 150°C

170s

Turn off UG, LG Turn off UG, LG TEMP < 130°C

VIN - VOUT > 0.2V

2ms

UG OCP = 0.3A

N/A

VIN - VOUT < 0.2V

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RT4823M
Absolute Maximum Ratings (Note 1)
VIN, VOUT, SW, EN, FPWM ---------------------------------------------------------------------------------------0.3V to 6.5V Power Dissipation, PD @ TA = 25°C WL-CSP-9B 1.3x1.2 (BSC) -----------------------------------------------------------------------------------------1.54W Package Thermal Resistance (Note 2) WL-CSP-9B 1.3x1.2 (BSC) -----------------------------------------------------------------------------------------64.9C/W Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------260C Junction Temperature ------------------------------------------------------------------------------------------------150C Storage Temperature Range ---------------------------------------------------------------------------------------65C to 150C ESD Susceptibility (Note 3)
HBM (Human Body Model) -----------------------------------------------------------------------------------------2kV

Recommended Operating Conditions (Note 4)
Input Voltage Range (Boost Mode) ------------------------------------------------------------------------------- 1.8V to 5.5V Output Voltage Range -----------------------------------------------------------------------------------------------5V Input Capacitor, CIN -------------------------------------------------------------------------------------------------- 4.7F Output Capacitor, COUT -------------------------------------------------------------------------------------------- 3.5F to 50F Inductance, L -----------------------------------------------------------------------------------------------------------0.7H to 2.2H Input Current (Average current into SW) -----------------------------------------------------------------------1.8A Input Current (Peak current into SW)-----------------------------------------------------------------------------4A Ambient Temperature Range --------------------------------------------------------------------------------------40C to 85C Junction Temperature Range --------------------------------------------------------------------------------------40C to 125C

Electrical Characteristics

(VIN = 3.6V, CIN = 4.7F, COUT = 10F, L1 = 1H. All typical (TYP) limits apply for TA = 25C, unless otherwise specified. All minimum (MIN) and maximum (MAX) apply over the full operating ambient temperature range (40C TA 85C).

Parameter

Symbol

Test Conditions

Min Typ Max Unit

Input Supply

VIN Operation Range

VIN

1.8

5.5 V

Into VIN Operating Quiescent Current

IQ(non-switching)

IOUT = 0mA, VIN = 3.6V, EN = FPWM = GND

0.1 0.5 A

Into VOUT Standby Mode Quiescent Current

IQ(non-switching)

3 A

VIN Quiescent Current (Device Normal Switching)

IQ(switching)

VIN = 3.6V, VOUT = 5V, FPWM = EN = GND
VIN = 3.6V, VOUT = 5V, FPWM = GND, EN = VIN

VIN = 3.6V, VOUT = 5V, FPWM = EN = VIN

-- mA

Power-On Reset

VPOR

1.2 1.5

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Parameter Enable, FPWM Low-Level Input Voltage High-Level Input Voltage
Input Leakage Current
OUTPUT

Symbol
VIL VIH Ilkg

Regulated DC Output Voltage VOUT

Output Discharge Resistor
Power Switch High-Side MOSFET Low-Side MOSFET Minimum On-Time
Maximum Duty Cycle
Switch Peak Current Limit (VIN or VOUT > 2.2V) Switch Valley Current Limit (VIN or VOUT > 2.2V) Pass-Through Current Limit Negative OCP Oscilator

RDISCHARGE
rDS_H rDS_L tON_MIN DMAX
ILIM(Peak)
ILIM(Valley) ILIM(Pass) ILIM(Neg)

Oscillator Frequency

fOSC

Soft-Start

Start-Up Time

tSTART_BST

Pre-Charge Current Limit Protection Short-Circuit Protection Over-Temperature Protection Over-Temperature Protection Hysteresis Over-Current Protection

ILIM(Start)
VSCP TOTP TOTP_HYS ILIM(5A)

Test Conditions

RT4823M
Min Typ Max Unit

Input connected to GND or VIN

0.4 V

1.2

0.5 A

1.8V VIN 4.8V, IOUT = 0mA, PFM operation

5.04

5.06

5.08

VIN = 3.6V, IOUT = 1A, PWM operation

4.95 5 5.05 V

VIN = 3.6V, EN = 0V

100

VIN = 1.8V to 4.8V, VOUT = 5V 20

VIN = 1.8V, VOUT = 5V, IL = 400mA

68.8 --

-- m -- m 60 ns

VIN = 3.6V, VOUT = 5V

-- 3900 -- mA

VIN = 3.6V, VOUT = 5V VIN = 3.6V

-- 3600 -- mA
250 300 350 mA 3000 2000 1000 mA

VIN = 3.6V

3.5

VIN < 2.5V start to reduce frequency

MHz --

VIN = 3.6V, BP = GND, IOUT = 0mA. Time from active EN to 100 400 500 s VOUT

VIN = 3.6V, EN = 0 1.8V

250 300 350 mA

VIN = 5V

0.5 0.7 0.9 V 140 150 160 C

-- C

5.5 A

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RT4823M
Parameter Efficiency
Efficiency

Symbol

Test Conditions

VOUT = 5V, VIN = 3.6V, Load = 10A
VOUT = 5V, VIN = 3.6V, Load = 10mA Eff VOUT = 5V, VIN = 3.6V, Load = 600mA
VOUT = 5V, VIN = 3.6V, Load = 1000mA

Min Typ Max Unit

Note 1. 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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability.
Note 2. JA is measured under natural convection (still air) at TA = 25°C with the component mounted on a high effective-thermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard. JC is measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precautions are recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.

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Typical Application Circuit

RT4823M

B1, B2

RT4823M

A1, A2

SW 1µH

VOUT

COUT VOUT

VIN

CIN

A3 VIN

10F

4.7F

B3 EN

C3 FPWM GND C1, C2

Reference CIN COUT L

Table 3. Recommended Components Information

Part Number

Description

Package

GRM155R60J475ME47D 4.7F/6.3V/X5R

0402

GRM188R60J106ME47D 10F/6.3V/X5R

0603

DFE252012F-1R0M=P2

1.0H/3.3A

2.5x2.0x1.2mm

Manufacturer Murata Murata Murata

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RT4823M
Typical Operating Characteristics
Efficiency vs. Output Current
100

Efficiency (%)

Output Voltage (V)

VIN : 4.5V

VIN : 3.6V 60
VIN : 3.3V

VIN : 2.5V

VIN : 1.8V

VOUT = 5V 20

0.001 0.01 0.1

100 1000

Output Current (mA)

5.50 5.40 5.30 5.20 5.10 5.00 4.90
2.4

Boost Line Regulation
IOUT : 0.01A IOUT : 0.1A IOUT : 0.5A IOUT : 0.8A

VOUT = 5V

3.0

3.6

4.2

4.8

5.4

6.0

Input Voltage (V)

Output Ripple vs. Output Current

120

COUT = 10F/6.3V (0603), X5R,

100

GRM188R60J106ME47D

VIN : 2.7V

VIN : 3.3V

VIN : 3.6V

VIN : 4.5V

0.00

0.01

0.10

1.00

Output Current (A)

Output Ripple (mV)

Maximum Output Current (A)1

Output Voltage (V)

Boost Load Regulation
5.20

5.15

5.10

5.05 VIN : 5V

5.00

VIN : 4.5V VIN : 3.6V

4.95

VIN : 2.5V VIN : 1.8V

4.90 0.001

0.010

0.100

VOUT = 5V

1.000

10.000

Output Current (A)

Maximum Output Current vs. Input Voltage
2.5

40°C

2.0

25°C

85°C

1.5

1.0

0.5
VOUT = 5V 0.0
1.8 2.2 2.6 3.0 3.4 3.8 4.2 4.6 5.0
Input Voltage (V)

Output Ripple vs. Output Current

120

COUT = x4 10F/6.3V (0402), X5R,

100

GRM155R60J106ME15

80 VIN : 2.7V

VIN : 3.3V

VIN : 3.6V

VIN : 4.5V

0.00

0.01

0.10

1.00

Output Current (A)

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RT4823M

Quiescent Current (A)

Quiescent Current vs. Input Voltage
18 VOUT = 5V, IOUT = 0mA, Boost mode
15

9 85°C

25°C

40°C

0 1.8 2.1 2.4 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8
Input Voltage(V)

Quiescent Current (A)

Quiescent Current vs. Input Voltage

VOUT = VIN, IOUT = 0mA, Bypass mode 35

85°C

25°C

40°C 25

0 2.2 2.5 2.8 3.1 3.4 3.7 4.0 4.3 4.6 4.9 5.2 5.5
Input Voltage (V)

Pre-Charge Current (mA)

Pre-Charge Current vs. Input Voltage
500 450 400 350 300 250 200 150 100
50 0 1.8 2.1 2.4 2.7 3.0 3.3 3.6 3.9 4.2 4.5
Input Voltage (V)

Pre-Charge Current (mA)

Pre-Charge Current vs. Temperature
400

350

300

250

VIN : 4.5V

200

VIN : 3.6V

VIN : 3.3V

150

VIN : 2.5V

100
VIN : 1.8V 50

0 -50 -25

25 50 75

Temperature (°C)

100 125

SW (4V/Div)
2
VOUT (1V/Div)

Boost Short Circuit
VIN = 3.6V, VOUT = 5V, IOUT = 0A

EN 2
(2V/Div)

Power-On
VIN = 3.6V, VOUT = 5V, IOUT = 0A

1
ILX
4
(1V/Div)

Time (0.01ms/Div)

VOUT (1V/Div) 1

ILX

(0.2V/Div)

Time (0.1ms/Div)

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RT4823M

Load Transient

VOUT (0.1V/Div)

VIN = 3.6V, VOUT = 5V, IOUT = 50mA to 500mA, tR = tF =10s

VOUT (0.1V/Div)

Load Transient
VIN = 3.6V, VOUT = 5V, IOUT = 0mA to 750mA, tR = tF =10s

IOUT (0.2V/Div) 3
VOUT (0.1V/Div)

Time (0.1ms/Div) Load Transient

IOUT 3
(0.2V/Div)

Time (0.1ms/Div)

VOUT (0.1V/Div)

Sine Waveform Stability
VIN = 3.6V, VOUT = 5V

IOUT (0.5V/Div)
3
VOUT (0.1V/Div)
SW (4A/Div)
2

VIN = 3.6V, VOUT = 5V, IOUT = 750mA to 1500mA,tR = tF =10s
Time (0.1ms/Div)
PFM Output Ripple
VIN = 3.6V, VOUT = 5V, IOUT = 0A

IOUT
3
(0.5V/Div)
VOUT (0.1V/Div)
SW (4A/Div)
2

Time (5ms/Div)
PFM Output Ripple
VIN = 4.5V, VOUT = 5V, IOUT = 0A

ILX 4
(0.4A/Div)

Time (20ms/Div)

ILX 4
(0.4A/Div)

Time (20ms/Div)

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RT4823M

VOUT (0.02V/Div)
SW (4V/Div)
2
ILX (0.4V/Div)
4

PWM Output Ripple

VIN = 3.6V, VOUT = 5V, IOUT = 0.5A
Time (0.0002ms/Div)

VOUT (0.02V/Div)
SW (4V/Div) 2
ILX (0.4V/Div)
4

PWM Output Ripple
VIN = 4.5V, VOUT = 5V, IOUT = 0.5A
Time (0.0002ms/Div)

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RT4823M
Application Information

Enable
The device can be enabled or disabled by the EN pin. When the EN pin is higher than the threshold of logic-high, the device starts operating with soft-start. Once the EN pin is set at low, the device will be shut down. In shutdown mode, the converter stops switching, internal control circuitry is turned off, and the load is disconnected from the input. This also means that the output voltage can drop below the input voltage during shutdown.

Power Frequency Modulation (PFM)
PFM is used to improve efficiency at light load. When the output voltage is lower than a set threshold voltage, the converter will operate in PFM. It raises the output voltage with several pulses until the loop exits PFM.

Thermal Shutdown
The device has a built-in temperature sensor which monitors the internal junction temperature. If the temperature exceeds the threshold, the device stops operating. As soon as the IC temperature has decreased below the threshold with a hysteresis, it starts operating again. The built-in hysteresis is designed to avoid unstable operation at IC temperatures near the over temperature threshold.

Inductor Selection

The point of inductor selection is the maximum loading of the application. The example is given by below application condition and equations. Application condition: VIN = 3V, VOUT = 5V, IOUT = 1.5A, converter efficiency = 81%, Frequency = 3.5MHz, L = 1H. Step 1 : To calculate input current (IIN).

IIN

VOUT IOUT VIN Eff

3.086A

Step 2 : To calculate duty cycle of boost converter.

D 1 VIN 0.4 VOUT

Step 3 : To calculate peak current of inductor.

IL(Peak)

IIN

0.5

VIN D L Freq.

3.258A

The recommended nominal inductance value is 1H. It is recommended to use inductor with dc saturation current 3300mA.

Input Capacitor Selection
At least a 4.7F and the rate voltage is 6.3V for DC bias input capacitor is recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit for SW. And input capacitor placed as close as possible to the VIN and GND pins of the IC is recommended.

Output Capacitor Selection
At least 10F capacitors is recommended to improve VOUT ripple. Output voltage ripple is inversely proportional to COUT. Output capacitor is selected according to output ripple which is calculated as :

VRIPPLE(PP)

tON

ILOAD COUT

and

tON

tSW

VIN VOUT

therefore :

COUT

tSW

VIN VOUT

ILOAD VRIPPLE(PP)

and

tSW

1 fSW

The maximum VRIPPLE occurs at minimum input voltage and maximum output load.

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Output Discharge Function
With the EN pin set to low, the VOUT pin is internally connected to GND by an internal discharge N-MOSFET switch. After the 10ms, IC will be true-shut down. This feature prevents residual charge voltages on capacitor connected to VOUT pins, which may impact proper power up of the system.
Current Limit
The RT4823M employs a valley-current limit detection scheme to sense inductor current during the off-time. When the loading current is increased such that the loading is above the valley current limit threshold, the off-time is increased until the current is decreased to valley-current threshold. Next on-time

RT4823M
begins after current is decreased to valley-current threshold. On-time is decided by (VOUT VIN) / VOUT ratio. The output voltage decreases when further loading current increase. The current limit function is implemented by the scheme, refer to Figure 2.
OCP (ILIM(5A)) Shutdown Protection
The RT4823M is implemented OCP shutdown protection. When the converter is operation in boost mode, peak current limit and valley current limit function can not protect IC from short circuit or the huge loading. The RT4823M is implemented truth disconnection function, when peak current is > 5A (Typ.), boost converter will turn off high-side MOSFET (UG) and low-side MOSFET (LG).

Inductor Current

DIL

VIN D Lf

IIN (DC)

Figure 2. Inductor Currents In Current Limit Operation

IIN (DC) Valley Current Limit

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RT4823M
Thermal Considerations
The junction temperature should never exceed the absolute maximum junction temperature TJ(MAX), listed under Absolute Maximum Ratings, to avoid permanent damage to the device. The maximum allowable power dissipation depends on the thermal resistance of the IC package, the PCB layout, the rate of surrounding airflow, and the difference between the junction and ambient temperatures. The maximum power dissipation can be calculated using the following formula :
PD(MAX) = (TJ(MAX) - TA) / JA
where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and JA is the junction-to-ambient thermal resistance.
For continuous operation, the maximum operating junction temperature indicated under Recommended Operating Conditions is 125°C. The junction-toambient thermal resistance, JA, is highly package dependent. For a WL-CSP-9B 1.3x1.2 (BSC) package, the thermal resistance, JA, is 64.9°C/W on a standard JEDEC 51-7 high effective-thermal-conductivity four-layer test board. The maximum power dissipation at TA = 25°C can be calculated as below :
PD(MAX) = (125°C - 25°C) / (64.9°C/W) = 1.54W for a WL-CSP-9B 1.3x1.2 (BSC) package.
The maximum power dissipation depends on the operating ambient temperature for the fixed TJ(MAX) and the thermal resistance, JA. The derating curves in Figure 3 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation.

Maximum Power Dissipation (W)1

2.0 Four-Layer PCB
1.6

1.2

0.8

0.4

0.0 0

100

125

Ambient Temperature (°C)

Figure 3. Derating Curve of Maximum Power Dissipation

Layout Considerations
The PCB layout is an important step to maintain the high performance of the RT4823M. Both the high current and the fast switching nodes demand full attention to the PCB layout to save the robustness of the RT4823M through the PCB layout. Improper layout might show the symptoms of poor line or load regulation, ground and output voltage shifts, stability issues, unsatisfying EMI behavior or worsened efficiency. For the best performance of the RT4823M, the following PCB layout guidelines must be strictly followed.
Place the input and output capacitors as close as possible to the input and output pins respectively for good filtering.
For thermal consider, it needed to maximize the pure area for power stage area besides the SW.

is a registered trademark of Richtek Technology Corporation.
DS4823M-00 July 2022

Layer 1 Layer 4
This capacitor is used to prevent input voltage ringing because of long wires.
VIN

RT4823M

GND

FPWM

GND

VIN

VOUT

Figure 4. PCB Layout Guide

is a registered trademark of Richtek Technology Corporation.
www.richtek.com 17

RT4823M
Outline Dimension

Symbol
A A1 b D D1 E E1 e

Dimensions In Millimeters

Min

Max

0.500

0.600

0.170

0.230

0.240

0.300

1.160

1.240

0.800

1.260

1.340

0.800

0.400

Dimensions In Inches

Min

Max

0.020

0.024

0.007

0.009

0.012

0.046

0.049

0.031

0.050

0.053

0.031

0.016

9B WL-CSP 1.3x1.2 Package (BSC)

is a registered trademark of Richtek Technology Corporation.
DS4823M-00 July 2022

Footprint Information

RT4823M

Package WL-CSP1.3x1.2-9(BSC)

Number of Pin
9

Type
NSMD SMD

Footprint Dimension (mm)

0.400

0.240 0.270

0.340 0.240

Tolerance ±0.025

Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789

Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.

is a registered trademark of Richtek Technology Corporation.
www.richtek.com 19

References

Richtek Technology