The XRP6124 is a non synchronous step-down (buck) controller for up to 5Amps point-of-loads. A wide 3V to 30V input voltage range allows for single supply operations from industry standard 3.3V, 5V, 12V and 24V power rails.
With a proprietary Constant On-Time (COT) control scheme, the XRP6124 provides extremely fast line and load transient response while the operating frequency remains nearly constant. It requires no loop compensation hence simplifying circuit implementation and reducing overall component count. The XRP6124 also implements an emulated ESR circuitry allowing usage of ceramic output capacitors and insuring stable operations without the use of extra external components.
Built in soft-start prevents high inrush currents while under voltage lock-out and output short-circuit protections insure safe operations under abnormal operating conditions.
The XRP6124 supports input voltages up to 18V while the XRP6124HV supports input voltages up to 30V. Both options are available in a RoHS compliant, green/halogen free space-saving 5-pin SOT23 package.
- 5A point-of-load capable step-down controller
- Down to 1.2V output voltage conversion
- Wide input voltage range
- 3V to 18V: XRP6124
- 4.5V to 30V: XRP6124HV
- Constant on-time operations – 500ns
- Up to 1MHz constant frequency operations
- No external compensation
- Supports ceramic output capacitors
- Fast transient response
- Built-in 2ms soft-start
- Short circuit protection
- <1µA shutdown current
- RoHS Compliant, Green/Halogen Free 5-pin SOT23 package
- Point-of-load conversions
- Audio-video equipment
- Industrial and medical equipment
- Distributed power architecture
Parts & Purchasing
|Part Number||Pkg Code||RoHS||Min Temp||Max Temp||Status||Buy Now||Order Samples|
Active - the part is released for sale, standard product.
EOL (End of Life) - the part is no longer being manufactured, there may or may not be inventory still in stock.
CF (Contact Factory) - the part is still active but customers should check with the factory for availability. Longer lead-times may apply.
PRE (Pre-introduction) - the part has not been introduced or the part number is an early version available for sample only.
OBS (Obsolete) - the part is no longer being manufactured and may not be ordered.
NRND (Not Recommended for New Designs) - the part is not recommended for new designs.
Frequently Asked Questions
Find the product page of the part that you want to get an evaluation board for and click on Parts & Purchasing. Example:
Find the icons under Buy Now or Order Samples:
Click on the Buy Now icon and see who has stock and click on the Buy button:
Alternatively, you can click on the Order Samples
If the icons are missing, then contact Customer Support.
In this example, we looked for XRA1201. Click on part number header or on the link at the bottom of the result. This brings you to the product page. For example:
Click on Parts & Purchasing, highlighted with the blue arrow above. The screen changes to:
Notice the status column and the “Show obsolete parts” link. A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers, the legend still present:
Another method to find out if a part is OBS or EOL is to click on SUPPORT at the top:
And then Product Change Notifications:
Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:
If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.
The COT families (XRP6141, XRP6124 and XR75100 controllers, XR76xxx regulators and XR79xxx power modules) have 2 modes of operation that can be set: DCM / CCM (discontinuous conduction mode / continuous conduction mode) or FCCM (Forced CCM) mode. In FCCM mode, the converter operates at a preset frequency regardless of output current. In DCM / CCM mode the converter operates in DCM or CCM depending on the Iout magnitude. If Iout < ½ Ipp, the converter transitions to DCM mode. If Iout is higher, operation is in CCM mode.
The main advantage of DCM / CCM is that it provides significantly higher efficiency at light loads. For those applications where that doesn’t matter, FCCM can be used and has the advantage that it allows for operation at a constant frequency, regardless of load. It also results in lower Vout ripple, and will operate in an inaudible range.
There are many factors to consider in selecting the inductor including core material, inductance versus frequency, current handling capability, efficiency, size and EMI. Typically, the inductor is primarily chosen for value, saturation current and DC resistance (DCR). Increasing the inductor value will decrease output voltage ripple, but degrade transient response. Low inductor values provide the smallest size, but cause large ripple currents, poor efficiency and require more output capacitance to smooth out the larger ripple current. The inductor must be able to handle the peak current at the switching frequency without saturating, and the copper resistance in the winding should be kept as low as possible to minimize resistive power loss. A good compromise between size, loss and cost is to set the inductor ripple current to be within 20% to 40% of the maximum output current.
The switching frequency and the inductor operating point determine the inductor value as follows:
L = Vout x (Vinmax – Vout) / Vinmax x fs x Kr x Ioutmax
Where fs = switching frequency
Kr = ratio of the AC inductor ripple current to the maximum output current
So for example, we want to choose L for the XR76108 (Ioutmax 8A) and wish to convert 12Vin to 2.5Vout with a frequency of 1MHz:
In our example, Ipp = 35% x 8A = 2.8A
Once the required inductor value is selected, the proper selection of core material is based on peak inductor current and efficiency requirements. The core must be large enough not to saturate at the peak inductor current.
Ipeak = Ioutmax + Ipp/2
In our example, Ipeak = 8A + 2.8A/2 = 9.4A
In general, it is set for Imax x 1.5. It would be close the maximum Iout (including ripple). If conservatively set too high, the hiccup mode may not be activated fast enough. If set too low, the ripple could cause the current to go over the threshold and set it into hiccup on a pre-mature basis.
A zero-cross comparator monitors the voltage across the low-side FET when it is on. The comparator threshold is nominally set at -1mV or -2mV (see individual datasheet). If there is sufficient IOUT such that VSW is below the threshold and therefore does not trigger the zero-cross comparator, CCM operation continues.
As IOUT is reduced, VSW gets closer to ground. When VSW meets the threshold, the zero-cross comparator triggers. If there are 8 consecutive triggers, then DCM operation begins. The low side FET is turned off when IL x RDS equals the zero-cross threshold.
As there is no negative inductor current, the charge transferred to COUT is preserved. As IOUT decreases further, less charge transfer to COUT is required. Pulses grow further apart, frequency is reduced and efficiency increases.
DCM persists as long as there are 8 consecutive zero-crosses.
Note that when the DCM frequency falls below about 1kHz, the controller turns on the lower-side FET for 100ns once every 1.2ms to refresh the charge on the bootstrap capacitor. This refresh cycle generates small spikes on SW, which can be seen interlaced between DCM pulses.