Ultra-Small Packages Shrink Power Management ICs

Torex Semiconductor Ltd. specializes in USP (Ultra Small Package) power management ICs primarily targeted toward battery powered and energy efficient applications. The Tokyo-based company employs CMOS analog technology for its core product offerings of LDO voltage regulators, voltage detectors and DC/DC converters housed in USPs and other small packages.

USP ICs have a resin-sealed leadless surface mount package with electroform transfer leads (Fig. 1). Because electroform transfer leads are used rather than lead frames that require an expensive mold, changes of lead shape are easily accomplished, and it is easy to modify the package to match the chip and functional objective, including the size, shape and number of pins. As such, this package offers a high degree of freedom.

Fig. 1. The USP (ultra-small package) is smaller, has a lower profile and better heat dissipation than comparable surface mount packages.

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The USP package can support a wide range of applications, including multi-chip packaging, bump chip packaging, and stacked-chip packaging. Compared to conventional surface mount packages, this package is smaller, has a lower profile, and better heat dissipation by means of exposure of the back surface leads. Although the package is thin and the back surface leads are exposed, a sufficient pin bonding strength is maintained by adding a pin lead overhang that hooks on to the resin.

Other packages that have the same shape and structure as the USP are PLP (Plated Lead Package) and DFN (Dual Flat Non Lead Package). The USP and PLP have the same basic structure and use electroformed leads for the electrode material. The DFN uses a lead frame. An advantage of electroformed leads is that they can be made thinner than a lead frame, 0.3 mm compared with about 0.6mm being the lowest possible profile achievable for each type. The electrical characteristics are roughly the same when the bonding is the same, although there are some structural differences.

Housed in a USP-10B package that measures 2.9 x 2.6 x 0.6 mm is the Torex XC9252 series of step-down DC/DC controllers intended for 30 V operation. It is a high breakdown voltage IC with a 30 V (nominal) input, and a peak of 46 V for 400 ms. Its input voltage range is from 3.0 V to 30 V, and its P-channel MOSFET driver provides a stable output voltage even with a low dropout voltage. Operating temperature range is from -40 °C up to +105 °C. It incorporates an 0.8 V reference, which allows output voltage can be set to any value from 1.5 V up using external resistors R_FB1and R_FB2(Fig. 2).

Fig. 2. The XC9252 is a controller IC that employs an external P-channel MOSFET output stage.

PWM/PFM auto switching control realizes high efficiency over the entire load range, from light to heavy loads. In the automatic PWM/PFM control mode the IC operates under PFM control for light loads.

An external resistor at the R_OSCpin sets the switching frequency to any value from 280 kHz to 550 kHz. Its MODE/SYNC pin can suppress unnecessary noise by synchronizing to an external clock within a range of ±25 % of the internal clock.

You can design general purpose products by selecting the appropriate external components for the specific application. Soft start time is adjustable by adding an external capacitor (C_SS) to the SS pin. Soft start time depends on the effective capacitance of C_SS. A UVLO (under voltage lockout) function forces the output driver to turn off if the input is 2.5 V or less.

Protection circuits include over-current, short-circuit and thermal shutdown. You can also add current limiting by inserting a resistor between V_INand I_SENSEpins (R_SENSEin Fig. 1). The limit current detection voltage varies according the operating temperature, so you should set the current limit using the lower limit value over the -40 to 105 °C temperature range.

These ICs comply with the EU RoHS Directive and are Pb-free.

Features:

Duty Cycle: 100%
Supports car batteries and 24 V inputs
Avoids the AM broadcast band using an external resistor for frequency adjustment
Incorporates an external clock synchronization
PWM and PFM/PWM auto switching are controlled by the MODE pin30 μA quiescent current

Efficiency is 90% at f=460 kHz, V_IN=13 V or 16 V, V_OUT= 5.7 V, and I_OUT= 2 A.

Also housed in a USP is the XCL213/XCL214 series of step-down “micro DC/DC” converters with integrated coil whose external dimensions are 2.5 mm x 3.2 mm x 1.0 mm. This converter achieves a level of miniaturization and profile reduction said to put it in the world’s smallest class for a load current of 1.5 A (Fig. 3). These converters help save board mounting area and reduce development time because a power circuit can be created by simply adding two ceramic capacitors as external components. The built-in coil simplifies the board layout, making it possible to minimize unwanted radiation noise and operational trouble.

Fig. 3. An internal inductor in the XCL213/XCL214 simplifies the circuit and minimizes noise and other operational trouble related to circuit wiring.

Operating input voltage range is 2.7 V to 5.5 V, and the output voltage is selectable from 0.8 to 3.6 V (accuracy ±2.0%) in steps of 0.05 V. Switching frequency is 3.0 MHz (accuracy ±15%), and PWM control (XCL213) or PWM/PFM auto switching control (XCL214) are selectable based on the control method. The XCL213/XCL214 series use HiSAT-COT, an original Torex term for high speed transient response. This makes it ideal for portable devices and digital devices that have a DDR or CPU memory requiring a fast transient response.

Another USP part is the XC8107/XC8108 series of power switches in a 1.8 x 2.0 x 0.6 mm USP-6C package. Its internal P-channel MOSFET has an 85 mΩ on-resistance. These switches are ideal for USB 2.0 and 3.0 applications, as well as power line distribution applications.

The XC8107 series (Fig. 4) includes an over-current limiting function with ±10% accuracy. The XC8108 series has a variable current limiting function that you can set from 0.9A to 2.4A using an external resistor. The input voltage range is 2.5 V to 5.5 V and the quiescent current is 40 μA (V_IN= 5.0 V).

Fig. 4. A flag output monitors the power switch status of the XC8107.XC8108. It outputs a low level signal when it detects over-current, overheating, or reverse current.

Protection circuits include current limiting, reverse current prevention, thermal shutdown, under-voltage lockout (UVLO) and soft start. Either of two types, an auto recovery type or a latch type, can be selected for the protection circuits. A flag function allows monitoring of the switch state. The flag pin is an N-channel open drain output MOSFET that outputs low level during detection of over-current or over-heating, or while the reverse current prevention function is operating. The operating temperature range is -40 °C to +105 °C.

This series is an environment-friendly product that complies with the EU RoHS Directive and is Pb-free.