Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPTH08T230WAZT

PTH08T230W, PTH08T231W

SLTS265L –NOVEMBER 2005– REVISED AUGUST 2011

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Designing for Fast Load Transients

The transient response of the dc/dc converter has been characterized using a load transient with a di/dt of

2.5 A/μs. The typical voltage deviation for this load transient is given in the Electrical Characteristics table using

the minimum required value of output capacitance. As the di/dt of a transient is increased, the response of a

converter’s regulation circuit ultimately depends on its output capacitor decoupling network. This is an inherent

limitation with any dc/dc converter once the speed of the transient exceeds its bandwidth capability.

If the target application specifies a higher di/dt or lower voltage deviation, the requirement can only be met with

additional low ESR ceramic capacitor decoupling. Generally, with load steps greater than 100 A/μs, adding

multiple 10 μF ceramic capacitors plus 10 × 1 μF, and numerous high frequency ceramics (≤ 0.1 μF) is all that is

required to soften the transient higher frequency edges. The PCB location of these capacitors in relation to the

load is critical. DSP, FPGA and ASIC vendors identify types, location and amount of capacitance required for

optimum performance. Low impedance buses, unbroken PCB copper planes, and components located as close

as possible to the high frequency devices are essential for optimizing transient performance.

Table 3. Input/Output Capacitors

(1)

Capacitor Characteristics Quantity

Max Output Bus

(2)

Max.

Capacitor Vendor,

Ripple

Working Value ESR Physical Input

Type Series (Style)

No Turbo-

Current Vendor Part No.

Voltage (µF) at 100 Size (mm) Bus

Turbo- Trans

at 85°C

kHz

Trans Cap Type

(3)

(Irms)

Panasonic

FC (Radial) 25 V 1000 43mΩ 1690mA 16 × 15 1 ≥ 2 N/R

(4)

EEUFC1E102S

FC (Radial) 25 V 820 38mΩ 1655mA 12 × 20 1 ≥ 1 N/R

(4)

EEUFC1E821S

FC (SMD) 35 V 470 43mΩ 1690mA 16 × 16,5 1 ≥ 1 N/R

(4)

EEVFC1V471N

FK (SMD) 35 V 1000 35mΩ 1800mA 16 ×16,5 1 ≥ 2 N/R

(4)

EEVFK1V102M

United Chemi-Con

PTB, Poly-Tantalum(SMD) 6.3 V 330 25mΩ 2600mA 7,3×4,3×2.8 N/R

(5)

1 ~ 4 C ≥ 2

(6)

6PTB337MD6TER (V

≤ 5.1V)

(7)

LXZ, Aluminum (Radial) 35 V 680 38mΩ 1660mA 12,5 × 20 1 1 ~ 3 N/R

(4)

LXZ35VB681M12X20LL

PS, Poly-Alum (Radial) 16 V 330 14mΩ 5060mA 10 × 12,5 1 1 ~ 3 B ≥ 2

(6)

16PS330MJ12

PS, Poly-Alum (Radial) 6.3 V 390 12mΩ 5500mA 8 × 12,5 N/R

(5)

1 ~ 2 B ≥ 1

(6)

6PS390MH11 (V

≤ 5.1V)

(7)

PXA, Poly-Alum (SMD) 16 V 330 14mΩ 5050mA 10 × 12,2 1 1 ~ 3 B ≥ 2

(6)

PXA16VC331MJ12TP

PXA, Poly-Alum (Radial) 10 V 330 14mΩ 4420mA 8 × 12,2 N/R

(5)

1 ~ 2 B ≥ 1

(6)

PXA10VC331MH12

Nichicon, Aluminum

PM (Radial) 25 V 1000 43mΩ 1520mA 18 × 15 1 ≥ 2 N/R

(4)

UPM1E102MHH6

HD (Radial) 35 V 470 23mΩ 1820mA 10 × 20 1 ≥ 2 N/R

(4)

UHD1V471HR

Panasonic, Poly-Aluminum 2.0 V 390 5mΩ 4000mA 7,3×4,3×4,2 N/R

(5)

N/R

(8)

B ≥ 2

(6)

EEFSE0J391R(V

≤ 1.6V)

(7)

(1) Capacitor Supplier Verification

Please verify availability of capacitors identified in this table. Capacitor suppliers may recommend alternative part numbers because of

limited availability or obsolete products.

RoHS, Lead-free and Material Details

See the capacitor suppliers regarding material composition, RoHS status, lead-free status, and manufacturing process requirements.

Component designators or part number deviations can occur when material composition or soldering requirements are updated.

(2) Additional output capacitance must include the required 200 μF of ceramic type.

(3) Required capacitors with TurboTrans. See the TurboTrans Application information for Capacitor Selection

Capacitor Types:

(a) Type A = (100 < capacitance × ESR ≤ 1000)

(b) Type B = (1,000 < capacitance × ESR ≤ 5,000)

(4) Aluminum Electrolytic capacitor not recommended for the TurboTrans due to higher ESR × capacitance products. Aluminum and higher

ESR capacitors can be used in conjunction with lower ESR capacitance.

(5) N/R – Not recommended. The voltage rating does not meet the minimum operating limits.

(6) Required capacitors with TurboTrans. See the TurboTrans Application information for Capacitor Selection

Capacitor Types:

(a) Type A = (100 < capacitance × ESR ≤ 1000)

(b) Type B = (1,000 < capacitance × ESR ≤ 5,000)

(7) The voltage rating of this capacitor only allows it to be used for output voltage that is equal to or less than 80% of the working voltage.

(8) N/R – Not recommended. The ESR value of this capacitor is below the required minimum when not using TurboTrans.