ZHCSQI1A November 2022 – November 2023 TPS92622-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 應(yīng)用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3
Feature Description
- 6.3.1 Power Supply (SUPPLY)
- 6.3.2 Enable and Shutdow(EN)
- 6.3.3 Constant-Current Output and Setting (INx)
- 6.3.4 Thermal Sharing Resistor (OUTx and RESx)
- 6.3.5 PWM Control (PWMx)
- 6.3.6 Supply Control
- 6.3.7 Diagnostics
- 6.3.8 FAULT Bus Output With One-Fails-All-Fail
- 6.3.9 FAULT Table
- 6.3.10 LED Fault Summary
- 6.3.11 IO Pins Inner Connection
- 6.4 Device Functional Modes
- 7 Application and Implementation
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
封裝選項
機(jī)械數(shù)據(jù) (封裝 | 引腳)
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DRR|12
訂購信息
7.2.1.2 Detailed Design Procedure
Step 1: Use Equation 4 to determine the current sensing resistor, R(SNSx).
where
- V(CS_REG) = 150 mV (typical)
- I(OUTx_Tot) = 130 mA
According to design requirements, output current for each channel is same so that the R(SNS1) = R(SNS2) = 1.15 Ω. Two resistors in parallel can be used to achieve equivalent resistance when sense resistor is not a standard decade resistance value.
Step 2: Design the current distribution between I(OUTx) and I(RESx), and use Equation 5 to calculate the current sharing resistor, R(RESx). The R(RESx) value actually decides the current distribution for I(OUTx) path and I(RESx) path. TI recommends the current sharing resistor R(RESx) to consume 50% of the total current at typical supply operating voltage.
where
- V(SUPPLY) = 12 V (typical)
- I(OUTx_Tot) = 130 mA
The calculated result for R(RESx) resistor value including R(RES1), R(RES2) is 85.4 Ω when V(OUTx) is typical 3 × 2.15 V = 6.45 V.
Step 3: Design the threshold voltage of SUPPLY to enable the LED open-circuit diagnostics, and calculate voltage divider resistor value for R1 and R2 on DIAGEN pin.
The maximum forward voltage of LED-string is 3 × 2.5 V = 7.5 V. To avoid the open-circuit fault reported in low-dropout operation conditions, additional headroom between SUPPLY and OUTx must be considered. The TPS92622-Q1 device must disable open-circuit detection when the supply voltage is below LED-string maximum forward voltage plus V(OPEN_th_rising) and V(CS_REG). Use Equation 6 to calculate the voltage divider resistor, R1 and R2 value.
where
- V(OPEN_th_rising) = 420 mV (maximum)
- V(CS_REG) = 156 mV
- VIL(DIAGEN) = 1.045 V (minimum)
- R2 = 10 kΩ (recommended)
The calculated result for R1 is 67.3 kΩ when V(OUTx) maximum voltage is 7.5 V and V(CS_REG) is 156 mV.
Step 4: Design the threshold voltage of SUPPLY to turn on and off each channel of LED, and calculate voltage divider resistor value for R3 and R4 on PWM input pin.
The minimum forward voltage of LED string is 3 × 1.9 V = 5.7 V. To make sure the current output on each of LED-string is normal, each LED-string must be turned off when SUPPLY voltage is lower than LED minimum required forward voltage plus dropout voltage between INx to OUTx and V(CS_REG). Use Equation 7 to calculate the voltage divider resistor, R3 and R4 value.
where
- V(DROPOUT) = 300 mV (typical)
- V(CS_REG) = 156 mV (maximum)
- VIH(PWM) = 1.26 V (maximum)
- R4 = 10 kΩ (recommended)
The calculated result for R3 is 38.9 kΩ when V(OUTx) minimum voltage is 5.7 V and V(CS_REG) is 156 mV.