IC STEP-DOWN SWIFT CONV 10-MSOP

TPS54040DGQ

Manufacturer Part NumberTPS54040DGQ
DescriptionIC STEP-DOWN SWIFT CONV 10-MSOP
ManufacturerTexas Instruments
SeriesSWIFT™, Eco-Mode™
TypeStep-Down (Buck)
TPS54040DGQ datasheet
 


Specifications of TPS54040DGQ

Internal Switch(s)YesSynchronous RectifierNo
Number Of Outputs1Voltage - Output0.8 ~ 39 V
Current - Output500mAFrequency - Switching100kHz ~ 2.5MHz
Voltage - Input3.5 ~ 42 VOperating Temperature-40°C ~ 150°C
Mounting TypeSurface MountPackage / Case10-MSOP Exposed Pad, 10-HMSOP, 10-eMSOP
Mounting StyleSMD/SMTDuty Cycle (max)98 %
Input / Supply Voltage (max)42 VInput / Supply Voltage (min)3.5 V
Maximum Operating Temperature+ 150 CMinimum Operating Temperature- 40 C
Output Current0.5 AOutput Voltage0.8 V to 39 V
Supply Current116 uASwitching Frequency2500 KHz
Dc To Dc Converter TypeStep DownPin Count10
Input Voltage42VSwitching Freq2500KHz
Package TypeHTSSOP EPOutput TypeAdjustable
Switching RegulatorYesMountingSurface Mount
Input Voltage (min)3.5VOperating Temperature ClassificationAutomotive
Lead Free Status / RoHS StatusLead free / RoHS CompliantPower - Output-
Other names296-24228-5  
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Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
The switching frequency of the TPS54040 is adjustable over a wide range from approximately 100kHz to
2500kHz by placing a resistor on the RT/CLK pin. The RT/CLK pin voltage is typically 0.5V and must have a
resistor to ground to set the switching frequency. To determine the timing resistance for a given switching
frequency, use
Equation 11
or the curves in
typically set the switching frequency as high as possible, but tradeoffs of the supply efficiency, maximum input
voltage and minimum controllable on time should be considered.
The minimum controllable on time is typically 130ns and limits the maximum operating input voltage.
The maximum switching frequency is also limited by the frequency shift circuit. More discussion on the details of
the maximum switching frequency is located below.
RT kOhm
sw kHz
SWITCHING FREQUENCY
vs
RT/CLK RESISTANCE HIGH FREQUENCY RANGE
2500
2000
1500
1000
500
0
0
25
50
75
100
RT/CLK - Clock Resistance - kW
Figure 39. High Range RT
Overcurrent Protection and Frequency Shift
The TPS54040 implements current mode control which uses the COMP pin voltage to turn off the high side
MOSFET on a cycle by cycle basis. Each cycle the switch current and COMP pin voltage are compared, when
the peak switch current intersects the COMP voltage, the high side switch is turned off. During overcurrent
conditions that pull the output voltage low, the error amplifier will respond by driving the COMP pin high,
increasing the switch current. The error amplifier output is clamped internally, which functions as a switch current
limit.
To increase the maximum operating switching frequency at high input voltages the TPS54040 implements a
frequency shift. The switching frequency is divided by 8, 4, 2, and 1 as the voltage ramps from 0 to 0.8 volts on
VSENSE pin.
The device implements a digital frequency shift to enable synchronizing to an external clock during normal
startup and fault conditions. Since the device can only divide the switching frequency by 8, there is a maximum
input voltage limit in which the device operates and still have frequency shift protection.
During short-circuit events (particularly with high input voltage applications), the control loop has a finite minimum
controllable on time and the output has a low voltage. During the switch on time, the inductor current ramps to
the peak current limit because of the high input voltage and minimum on time. During the switch off time, the
inductor would normally not have enough off time and output voltage for the inductor to ramp down by the ramp
up amount. The frequency shift effectively increases the off time allowing the current to ramp down.
Copyright © 2009, Texas Instruments Incorporated
DETAILED DESCRIPTION (continued)
Figure 39
or
Figure
RT/CLK RESISTANCE LOW FREQUENCY RANGE
500
V = 12 V,
I
T = 25°C
J
400
300
200
100
0
200
125
150
175
200
Product Folder Link(s):
TPS54040
TPS54040
SLVS918 – MARCH 2009
40. To reduce the solution size one would
SWITCHING FREQUENCY
vs
V = 12 V,
I
T = 25°C
J
300
400
500
600
700
800
900
1000 1100
RT/CLK - Resistance - kW
Figure 40. Low Range RT
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