Document
RT4812
High Efficiency Boost Converter
General Description
The RT4812 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 RT4812 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 2.1A. Quiescent current in Shutdown Mode is less than 1A, which maximizes battery life.
Ordering Information
RT4812
Package Type J8F : TSOT-23-8 (FC) Lead Plating System G : Green (Halogen Free and Pb Free)
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.
Features
CMCOT Topology and Small Output Ripple when VIN close VOUT Voltage
Operates from a Single Li-ion Cell : 1.8V to 5.5V Adjustable Output Voltage : 1.8V to 5.5V PSM Operation Up to 96% Efficiency Boost Current Limit Output Over-Voltage Protection Pin Adjustable Average Output Current Limit
Threshold (2 Levels) Internal Compensation Output Discharge Output Short Protection True Load Disconnect
Applications
Single-Cell Li-Ion, LiFePO4 Smart-Phones Portable Equipment
Marking Information
0L=DNN
0L= : Product Code DNN : Date Code
Simplified Application Circuit
RT4812
L1
VIN
SW
VOUT
VOUT
C1
R1
C3
VIN C2
FB R2
EN
R3 H/L
ILIM GND
Copyright © 2022 Richtek Technology Corporation. All rights reserved.
DS4812-09 March 2022
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 1
RT4812
Pin Configuration
ILIM EN SW GND
(TOP VIEW)
87 6 5 2 34
VIN FB VOUT PGND
TSOT-23-8 (FC)
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
VIN
Power input. Input capacitor CIN must be placed as close to IC as possible.
2
FB
Voltage feedback.
3
VOUT
Boost converter output.
4
PGND
Power ground.
5
GND
Analog ground.
6
SW
Switching node.
7
EN
Enable input (1 enabled, 0 disabled), must not be floating.
8
ILIM
Average output current limit control pin. (H/L)
Functional Block Diagram
VOUT
VIN
SW Control
Gate
ILIM
OCP
DRV
SW
EN PGND
Digital CTRL
PWM CTRL
OSC
OTP
UVLO
AMP +
VREF
FB GND
Copyright © 2022 Richtek Technology Corporation. All rights reserved.
www.richtek.com 2
is a registered trademark of Richtek Technology Corporation.
DS4812-09 March 2022
Operation
The RT4812 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 a maximum load current of 2.1A. Quiescent current in Shutdown mode is less than 1A, which maximizes battery life.
Mode LIN 1
LIN LIN 2
Soft-Start Boost
Depiction Linear startup 1 Linear startup 2 Boost soft-start Boost mode
Condition VIN > VOUT VIN > VOUT VOUT < VOUT(MIN) VOUT = VOUT(MIN)
LIN State
When VIN is rising, it enters the LIN State. There are two parts for the LIN state. It provides maximum current for 1A to charge the COUT in LIN1, and the other one is for 3A in LIN2. By the way, the EN is pulled high and VIN > UVLO.
As the figure shown, if the timeout is over the specification, it will enter the Fault mode.
EN = 1, Vin > UVLO
LIN 1 Timeout < 512μs Timeout > 512μs
Soft-Start
LIN 2
Timeout < 1024μs Timeout > 1024μs
Boost mode
Fault State
Figure 1. RT4812 State Chart
RT4812
Startup and Shutdown State When VIN is rising and through the LIN state, it will enter the Startup state. If EN is pulled low, any function is turned-off in shutdown mode.
Soft-Start State It starts to switch in Soft-start state. After the LIN state, output voltage is rising with the internal reference voltage.
Fault State As the Figure 1 shown, it will enter to the Fault state as below, The timeout of LIN2 is over the 1024s. It will be the high impedance between the input and output when the fault is triggered. A restart will be start after 20ms.
OCP The converter senses the current signal when the high-side P-MOSFET turns on. As a result, the OCP is cycle-by-cycle current limitation. If the OCP occurs, the converter holds off the next on pulse until inductor current drops below the OCP limit.
OTP The converter has an over-temperature protection. When the junction temperature is higher than the thermal shutdown rising threshold, the system will be latched and the output voltage will no longer be regulated until the junction temperature drops under the falling threshold.
Input Voltage POR (Power-On Reset) The RT4812 is implemente.