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The TD7590 is a 240 KHz fixed frequency
monolithic step down switch mode regulator
with a built in internal Power MOSFET. It
achieves 5A continuous output current over a
wide input supply range with excellent load
and line regulation.
The device includes a voltage reference,
oscillation circuit, error amplifier, internal
PMOS and etc.
The PWM control circuit is able to adjust the
duty ratio linearly from 0 to 100%. An enable
function, an over current protection function
and a short circuit protection function are
built inside. An internal compensation block
is built in to minimize external component
count.
The TD7590 serves as ideal power supply
units for portable devices.
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| TO263-5L |
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| TO263-5L |
| Pin Number | Pin Name | Description |
| 1 | Vin | Supply Voltage Input Pin. TD7590 operates from a 3.6V to 36V DC voltage. Bypass Vin to GND with a suitably large capacitor to eliminate noise on the input. |
| 3 | Output | Power Switch Output Pin. SW is the switch node that supplies power to the output. |
| 2 | Gnd | Ground Pin. Care must be taken in layout. This pin should be placed outside of the Schottky Diode to output capacitor ground path to prevent switching current spikes from inducing voltage noise into TD7590. |
| 4 | Feedback | Feedback Pin. Through an external resistor divider network, FB senses the output voltage and regulates it. The feedback threshold voltage is 1.222V. |
| 5 | EN | Enable Pin. EN is a digital input that turns the regulator on or off .Drive EN pin high to turn on the regulator, drive it low to turn it off. |
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Input Voltage | VIN | -0.3 to 36 | V |
| Feedback Pin Voltage | VFB | -0.3 to Vin | V |
| Enable Pin Voltage | VEN | -0.3 to 12 | V |
| Switch Pin Voltage) | VSW | -0.3 to Vin | V |
| Output Power Limited | PD | 36 | W |
| Operating Junction Temperature | TJ | 150 | °C |
| Storage Temperature | TSTG | -65 to 150 | °C |
| Lead Temperature (Soldering, 10 sec) | TLEAD | 260 | °C |
| ESD(HBM) | VESD | 2000 | V |
| Thermal Resistance-Junction to Ambient | RθJA | 23 | °C/W |
| Thermal Resistance-Junction to Case | RθJC | 3.5 | °C/W |
| Parameter | Symbol | Min. | Max. | Unit |
|---|---|---|---|---|
| Input Voltage | VIN | 3.6 | 36 | V |
| Operating Junction Temperature | TJ | -40 | 125 | °C |
| Operating Ambient Temperature | TA | -40 | 85 | °C |
| Parameters | Symbol | Test Condition | Min | Typ. | Max. | Unit |
|---|---|---|---|---|---|---|
Input voltage |
VIN | 3.6 | 36 | V | ||
| Shutdown Supply Current | ISTBY | VEN=0V | 30 | 92 | uA | |
| Supply Current | ICC | VEN=2V, VFB=1.3V | 3.6 | 4 | mA | |
| Feedback Voltage | VFB | VIN=3.6V to 23V | 1.185 | 1.222 | 1.26 | V |
| Feedback Bias Current | IFB | VFB=1.3V | 0.1 | 0.5 | uA | |
| Switch Current Limit | ILIM | 6 | 6.5 | A | ||
| Switch Current Limit | FOSC | 200 | 240 | 280 | KHz | |
| Oscillator Frequency | FOSC1 | VFB=0V | 42 | KHz | ||
| Frequency of Current Limit or Short Circuit Protection |
VEN | 0.7 | 1.2 | 1.7 | V | |
| EN Pin Threshold | IH | VEN=2.5V | -0.1 | -1 | uA | |
| EN Pin Input Leakage Current |
IL | VEN=0.5V | -3 | -10 | uA | |
| Internal PMOS RDSON | RDSON | VIN=12V,VFB=0V VEN=12V,IOUT=5A |
80 | mΩ | ||
| Max. Duty Cycle | DMAN | VFB=0V,ISW=0.1V | 100 | % | ||
| Efficiency | η | VIN=12V,VOUT=5V IOUT=5A |
- | 92 | - | % |
| Thermal Shutdown | TOTSD | 165 | °C |
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| Figure 4. Switching Frequency vs. Temperature | Figure 5. Vfb vs. Temperature |
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| Figure 6. Icc vs. Temperature | Figure 7. Efficiency vs. Load (Vin=10V) |
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Figure 8. Typical Application of TD7590 for 5V/5A (Ceramic COUT) |
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Figure 9. Typical Application of TD7590 for 5V/5A (Electrolytic COUT) |
| Vin (Max) |
2A Load Current | 3A Load Current | ||||
|---|---|---|---|---|---|---|
| Part Number | Package | Vendor | Part Number | Package | Vendor | |
| 20V | B220/A | SMB/SMA | 1 | B320/B/A | SMC/B/A | 1 |
| SS22 | SMA | 2,3 | SS32 | SMC | 2,3 | |
| MBRS320 | SMC | 4 | ||||
| SK32 | SMC | 6 | ||||
| IN5820 | D0-201AD | 6 | ||||
| 30V | B230/A | SMB | 1 | B330/B/A | SMC/B/A | 1 |
| SS23 | SMB | 2,3 | SS33 | SMC | 2,3 | |
| 20BQ030 | SMB | 4 | MBRS330 | SMC | 4,5 | |
| MBRS230 | SMB | 5 | SK33 | SMC | 3,6 | |
| SK23 | SMB | 6 | IN5821 | D0-201AD | 2,6 | |
| 40V | B240/A | SMB/SMA | 1 | B340/B/A | SMC/B/A | 1 |
| SS24 | SMB | 1,3,5 | SS34 | SMC | 2,3 | |
| MBRS240 | SMB | 5 | Q0BQ040 | SMC | 4 | |
| MBRS340TR | SMC | 4,5 | ||||
| SK34 | SMC | 6 | ||||
| IN5822 | D0-201AD | 6 | ||||
| 50V | B250 A | SMB/SMA | 1 | B350/B/A | SMC/B/A | 1 |
| SS25 | SMB | 2,3 | SS35 | SMC | 2,3 | |
| SK23 | SMB | 5 | MBRS330 | SMC | 4,5 | |
| SK35 | SMC | 3.6 | ||||
| Vin (Max) |
4A Load Current | 5A Load Current | ||||
|---|---|---|---|---|---|---|
| Part Number | Package | Vendor | Part Number | Package | Vendor | |
| 20v | SL42 | SMC | 2,3 | B520C | SMC | 1 |
| SR502 | DO-201AD | 1 | ||||
| SB520 | DO-201AD | 2 | ||||
| IN5823 | DO-201AD | 6 | ||||
| 30V | SL43 | SMC | 2,3 | B530C | SMC | 1 |
| SR503 | DO-201AD | 1 | ||||
| SB530 | DO-201AD | 2 | ||||
| SSC53L | SMC | 3 | ||||
| IN5824 | D0-201AD | 6 | ||||
| 40V | SL44 | SMC | 2,3,5 | B540C | SMC | 1 |
| SR504 | DO-201AD | 1 | ||||
| SB540 | DO-201AD | 2 | ||||
| SSC54 | SMC | 3 | ||||
| IMBRS540T3 | SMC | 5 | ||||
| IN5825 | DC-201AD | 6 | ||||
| 50V | B550C | DC-201AD | 6 | |||
| SB550 | SMC | 1 | ||||
| DC-201AD | 2 | |||||
| No. | Vendor | Web Site |
|---|---|---|
| 1 | Diodes,Inc. | www.diodes.com |
| 2 | Fairchild Semiconductor | www.fairchildsemi.com |
| 3 | General Semiconductor | www.gensemi.com |
| 4 | nternational Rectifier | www.irf.com |
| 5 | On Semiconductor | www.onsemi.com |
| 6 | Pan Jit International | www.panjit.com.tw |
Output Voltage VS R1, R2 Resistor Selection Guide
Vout = (1+R1/R2)*1.222V
| Vout | R1 | R2 |
|---|---|---|
| 1.8V | 3.9K | 8.2K |
| 2.5V | 3.2K | 3K |
3.3V |
6.2K | 3.6K |
| 5V | 6.2K | 2K |
| 9V | 13K | 2K |
| 12V | 16K | 1.8K |
This is the positive input supply for the IC
switching regulator. A suitable input bypass
capacitor must be present at this pin to minimize
voltage transients and to supply the switching
currents needed by the regulator
Circuit ground.
Senses the regulated output voltage to complete the feedback loop.
Allows the switching regulator circuit to be
shutdown using logic level signals thus dropping
the total input supply current to approximately
30uA. Pulling this pin below a threshold voltage of
approximately 0.7 V turns the regulator down, and
pulling this pin above 1.3V (up to a maximum of12V) shuts the regulator on. For automatic starup
condition , can be implemented by the addition of
a resistive voltage divider from VIN to GND.
Thermal Considerations
The TD7590 (TO-263 package) junction
temperature rise above ambient temperature with
a 5A load for various input and output voltages.
This data was taken with the circuit operating as a
buck switching regulator with all components
mounted on a PC board to simulate the junction
temperature under actual operating conditions.
This curve can be used for a quick check for the
approximate junction temperature for various
conditions, but be aware that there are many
factors that can affect the junction temperature.
When load currents higher than 5A are used,
double sided or multilayer PC boards with large
copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages.
For the best thermal performance, wide copper
traces and generous amounts of printed circuit
board copper should be used in the board layout.
(Once exception to this is the output (switch) pin,
which should not have large areas of copper.)
Large areas of copper provide the best transfer of
heat (lower thermal resistance) to the surrounding
air, and moving air lowers the thermal resistance
even further.
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB. The
voltage divider divides the
output voltage down by the ratio:
VFB = VOUT * R2 / (R1 + R2)
Thus the output voltage is:
VOUT = 1.222 * (R1 + R2) / R2
R2 can be as high as 100KΩ, but a typical
value is 10KΩ. Using that value, R1 is
determined by:
R1 ~= 8.18 * (VOUT – 1.222) (KΩ)
For example, for a 3.3V output voltage, R2 is
10KΩ, and R1 is 17KΩ.
Inductor
The inductor is required to supply constant
current to the output load while being driven by
the switched input voltage. A larger value
inductor results in less ripple current that in
turn results in lower output ripple voltage.
However, the larger value inductor has a larger
physical size, higher series resistance, and/or
lower saturation current. Choose an inductor
that does not saturate under the worst-case
load conditions. A good rule for determining
the inductance is to allow the peak-to-peak
ripple current in the inductor to be approximately
30% of the maximum load
current. Also, make sure that the peak
inductor current (the load current plus half the
peak-to-peak inductor ripple current) is below
the TBDA minimum current limit. The
inductance value can be calculated by the
equation:
L = (VOUT) * (VIN-VOUT) / VIN * f * ΔI
Where VOUT is the output voltage, VIN is the
input voltage, f is the switching frequency, and ΔI is the peak-to-peak inductor ripple current.
Input Capacitor
The input current to the step-down converter is
discontinuous, and so a capacitor is required
to supply the AC current to the step-down
converter while maintaining the DC input
voltage. A low ESR capacitor is required to
keep the noise at the IC to a minimum.
Ceramic capacitors are preferred, but tantalum
or low-ESR electrolytic capacitors may also
suffice.
The input capacitor value should be greater
than 10μF. The capacitor can be electrolytic,
tantalum or ceramic. However since it absorbs
the input switching current it requires an
adequate ripple current rating. Its RMS current
rating should be greater than approximately
1/2 of the DC load current.
For insuring stable operation should be
placed as close to the IC as possible.
Alternately a smaller high quality ceramic
0.1μF capacitor may be placed closer to the IC
and a larger capacitor placed further away. If
using this technique, it is recommended that
the larger capacitor be a tantalum or
electrolytic type. All ceramic capacitors should
be places close to the TD7590.
Output Capacitor
The output capacitor is required to maintain
the DC output voltage. Low ESR capacitors
are preferred to keep the output voltage ripple
low. The characteristics of the output
capacitor also affect the stability of the
regulation control system. Ceramic, tantalum,
or low ESR electrolytic capacitors are
recommended. In the case of ceramic
capacitors, the impedance at the switching
frequency is dominated by the capacitance,
and so the output voltage ripple is mostly
independent of the ESR. The output voltage
ripple is estimated to be:
VRIPPLE ~= 1.4 * VIN * (fLC/fSW)^2
Where VRIPPLE is the output ripple voltage, VIN
is the input voltage, fLC is the resonant
frequency of the LC filter, fSW is the switching
frequency. In the case of tanatalum or low-
ESR electrolytic capacitors, the ESR
dominates the impedance at the switching
frequency, and so the output ripple is
calculated as:
VRIPPLE ~= ∆I * RESR
Where VRIPPLE is the output voltage ripple, ∆I is
the inductor ripple current, and RESR is the
equivalent series resistance of the output
capacitors.
Output Rectifier Diode
The output rectifier diode supplies the current
to the inductor when the high-side switch is off.
To reduce losses due to the diode forward
voltage and recovery times, use a Schottky
rectifier.
Table 1 provides the Schottky rectifier part
numbers based on the maximum input voltage
and current rating.
Choose a rectifier who’s maximum reverse
voltage rating is greater than the maximum
input voltage, and who’s current rating is
greater than the maximum load current.
Feedforward Capacitor (CFF)
For output voltages greater than approximately
8V, an additional capacitor is required. The
compensation capacitor is typically between 100
pF and 33 nF, and is wired in parallel
with the output voltage setting resistor, R1. It
provides additional stability for high output
voltages, low input-output voltages, and/or very
low ESR output capacitors, such as solid
tantalum capacitors.
CFF=1/(31x103xR1)
This capacitor type can be ceramic, plastic, silver
mica, etc.(Because of the unstable characteristics
of ceramic capacitors made with Z5U material,
they are not recommended.)
Note:In PCB layout. Reserved an area for CFF.
Over Current Protection (OCP)
The cycle by cycle current limit threshold is set
between 6A and 6.5A. When the load current
reaches the current limit threshold, the cycle by
cycle current limit circuit turns off the high side
switch immediately to terminate the current duty
cycle. The inductor current stops rising. The cycle
by cycle current limit protection directly limits
inductor peak current. The average inductor
current is also limited due to the limitation on peak
inductor current. When the cycle by cycle current
limit circuit is triggered, the output voltage drops
as the duty cycle is decreasing.
Thermal Management and LayoutConsideration
In the TD7590 buck regulator circuit, high pulsing
current flows through two circuit loops. The firstloop starts from the input capacitors, to the VIN
pin, to the VOUT pins, to the filter inductor, to the
output capacitor and load, and then returns to the
input capacitor through ground.
Current flows in the first loop when the high side
switch is on. The second loop starts from the
inductor, to the output capacitors and load, to the
GND pin of the TD7590, and to the VOUT pins of
the TD7590. Current flows in the second loop
when the low side diode is on.
In PCB layout, minimizing the two loops area
reduces the noise of this circuit and improves
efficiency. A ground plane is recommended to
connect input capacitor, output capacitor, and
GND pin of the TD7590.
In the TD7590 buck regulator circuit, the two
major power dissipating components are the
TD7590 and output inductor. The total power
dissipation of converter circuit can be measured
by input power minus output power.
Ptotal _loss = VIN× IIN– VO× IO
The power dissipation of inductor can be
approximately calculated by output current and
DCR of inductor.
Pinductor _loss= IO2 ×Rinductor × 1.1
The junction to ambient temperature can be got
from power dissipation in the TD7590 and thermal
impedance from junction to ambient.
T (jun-amb) =(Ptotalloss–Pinductorloss)× ΘJA
The maximum junction temperature of TD7590 is 145°C, which limits the maximum load current
capability. Please see the thermal de-rating
curves for the maximum load current of the
TD7590 under different ambient temperatures.
The thermal performance of the TD7590 is trongly
affected by the PCB layout. Extra care should be
taken by users during the design process to nsure
that the IC will operate under the recommended
environmental conditions.
Several layout tips are listed below for the best
electric and thermal performance.
1. Do not use thermal relief connection to the VIN
and the GND pin. Pour a maximized copper area
to the GND pin and the VIN pin to help thermal
dissipation.
2. Input capacitor should be connected to the VIN
pin and the GND pin as close as possible.
3. Make the current trace from VOUT pins to L to
the GND as short as possible.
4. Pour copper plane on all unused board area
and connect it to stable DC nodes, like VIN, GND,
or VOUT.
5. Keep sensitive signal traces such as trace
connecting FB pin away from the VOUT pins.
Package Information (TO263-5L)
| Symbol | Dimensions In Millimeters | Dimensions In Inches | ||
|---|---|---|---|---|
| Min. | Max. | Min. | Max. | |
| A | 4.06 | 4.83 | 0.16 | 0.19 |
| B | 0.76 | 1.02 | 0.03 | 0.04 |
| C | 0.36 | 0.64 | 0.014 | 0.025 |
| C2 | 1.14 | 1.4 | 0.045 | 0.055 |
| D | 8.64 | 9.65 | 0.34 | 0.38 |
| E | 9.78 | 10.54 | 0.385 | 0.415 |
| e | 1.57 | 1.85 | 0.062 | 0.073 |
| F | 6.6 | 7.11 | 0.26 | 0.28 |
| L | 15.11 | 15.37 | 0.595 | 0.605 |
| L2 | - | 1.4 | - | 0.055 |