SLPA021 November   2024 CSD13303W1015 , CSD16301Q2 , CSD16321Q5 , CSD16322Q5 , CSD16323Q3 , CSD16325Q5 , CSD16327Q3 , CSD16340Q3 , CSD16342Q5A , CSD16401Q5 , CSD16403Q5A , CSD16404Q5A , CSD16406Q3 , CSD16407Q5 , CSD16408Q5 , CSD16409Q3 , CSD16410Q5A , CSD16411Q3 , CSD16412Q5A , CSD16413Q5A , CSD16414Q5 , CSD16415Q5 , CSD16556Q5B , CSD17301Q5A , CSD17302Q5A , CSD17303Q5 , CSD17304Q3 , CSD17305Q5A , CSD17306Q5A , CSD17307Q5A , CSD17308Q3 , CSD17309Q3 , CSD17310Q5A , CSD17311Q5 , CSD17312Q5 , CSD17313Q2 , CSD17322Q5A , CSD17327Q5A , CSD17381F4 , CSD17501Q5A , CSD17505Q5A , CSD17506Q5A , CSD17507Q5A , CSD17510Q5A , CSD17522Q5A , CSD17527Q5A , CSD17551Q3A , CSD17551Q5A , CSD17552Q3A , CSD17552Q5A , CSD17553Q5A , CSD17555Q5A , CSD17556Q5B , CSD17559Q5 , CSD18501Q5A , CSD18502KCS , CSD18502Q5B , CSD18503KCS , CSD18503Q5A , CSD18504KCS , CSD18504Q5A , CSD18531Q5A , CSD18532KCS , CSD18532NQ5B , CSD18532Q5B , CSD18533KCS , CSD18533Q5A , CSD18534KCS , CSD18534Q5A , CSD18537NKCS , CSD18537NQ5A , CSD18563Q5A , CSD22202W15 , CSD25211W1015 , CSD25213W10 , CSD75207W15 , CSD86311W1723 , CSD86330Q3D , CSD86350Q5D , CSD86360Q5D , CSD87312Q3E , CSD87330Q3D , CSD87331Q3D , CSD87350Q5D , CSD87351Q5D , CSD87351ZQ5D , CSD87352Q5D , CSD87353Q5D , CSD87381P , CSD87588N

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Review the Data Sheet Limits
  6. 3Application-specific FETs
  7. 4Gate Drive Voltage Specifications
    1. 4.1 Absolute maximum VGS
    2. 4.2 Gate-to-source Threshold Voltage, VGS(th)
  8. 5High-side and Low-side Switches
    1. 5.1 Driving a High-side N-channel FET
    2. 5.2 Driving a Low-side N-channel FET
    3. 5.3 Driving a High-side P-channel FET
  9. 6Use a Gate-to-source Resistor
  10. 7Lowest RDS(on)≠ Lowest Power Loss
  11. 8Summary
  12. 9References

4.2 Gate-to-source Threshold Voltage, VGS(th)

The gate-to-source threshold voltage, VGS(th) is specified at ID = 250µA in TI FET data sheets. This is where the FET just begins to conduct current and is lower than the minimum VGS where RDS(on) is specified in the data sheet. For example, as shown in Table 4-4, typical VGS(th) = 1.75V for the CSD18541F5 60V N-channel FET but the minimum VGS = 4.5V where RDS(on) is specified in the data sheet.

Table 4-4 CSD18541F5 Electrical Characteristics TA = 25°C (unless otherwise stated)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
STATIC CHARACTERISTICS
BVDSS Drain-to-source voltage VGS = 0V, IDS = 250μA 60 V
IDSS Drain-to-source leakage current VGS = 0V, VDS = 48V 1 µA
IGSS Gate-to-source leakage current VDS = 0V, VGS = 20V 10 µA
VGS(th) Gate-to-source threshold voltage VDS = VGS, IDS = 250μA 1.4 1.75 2.2 V
RDS(on) Drain-to-source on-resistance VGS = 4.5V, IDS = 1A 57 75 mΩ
VGS = 10V, IDS = 1A 54 65
gfs Transconductance VDS = 6V, IDS = 1A 7.7 S
DYNAMIC CHARACTERISTICS
Ciss Input capacitance VGS = 0V, VDS = 30V,
ƒ = 1MHz		 598 777 pF
Coss Output capacitance 47 61 pF
Crss Reverse transfer capacitance 8.1 10.5 pF
RG Series gate resistance 1200 1600 Ω
Qg Gate charge total (10V) VDS = 30V, IDS = 1A 11 14 nC
Qgd Gate charge gate-to-drain 1.6 nC
Qgs Gate charge gate-to-source 1.5 nC
Qg(th) Gate charge at Vth 0.8 nC
Qoss Output charge VDS = 30V, VGS = 0V 3.2 nC
td(on) Turnon delay time VDS = 30V, VGS = 4.5V,
IDS = 1A, RG = 0Ω		 572 ns
tr Rise time 540 ns
td(off) Turnoff delay time 1076 ns
tf Fall time 496 ns
DIODE CHARACTERISTICS
VSD Diode forward voltage ISD = 1A, VGS = 0V 0.8 1 V

A common mistake is assuming as long as VGS≥ VGS(th), the FET is on and operates as intended in the application. This is not always the case. To ensure RDS(on) meets the data sheet limits, VGS must always be greater than or equal to the minimum value where RDS(on) is specified in the data sheet. This is often overlooked and can cause unexpected problems in the application. A customer using the CSD18541F5 had to change the design because the application used VGS = 3.3V instead of VGS = 4.5V. As shown in Figure 4-1, operating the CSD18541F5 with VGS < 4.5V, the slope of the curve is almost vertical and small changes in VGS(th) can result in exponential changes in RDS(on).

CSD18541F5 RDS(on) vs. VGS Figure 4-1 CSD18541F5 RDS(on) vs. VGS