Application Intermediate Bus Architecture Distributed Power Architecture Datacom Telecom Server, Workstation Benefits High Efficiency - No Heat Sink Required Reduction Overall Solution Board Area Tape and Reel Compatible with Pick and Place Equipment Minimize Part Numbers in Inventory Low Cost Product: Y-Series Features Available up to 5A (28W) Extended input range 9.6V - 14V No derating up to 85°C (70°C at 5V and 3.3V) Surface mount package Industry standard package and pinout Small profile Low profile: 0.80 "x 0.45" x 0.247" (20.32mm x 11.43mm x 6.27mm) Weight: 0.079 oz [2.26 g] Coplanarity < 0.003" Synchronous Buck Converter Topology Start-Up to Pre-Biased Output No Minimum Load Available via External Resistor Enables programmable output voltage Operating ambient temperature: -40°C to 85°C remote on/off Fixed frequency operation Automatic reset Output overcurrent protection Million Hours, Method I Case 1 All materials meet UL94, V-0 flammability rating UL 60950 for the US and Canada and DEMKO for IEC/EN 60950 (pending) Lead-Free/RoHS Compliant Design RoHS Compliant

Description: The Y-Series non-isolated DC-DC converters provide up to 5 amps of output current in an industry standard SurfaceMont package. The YM12S05 converter operates at an input voltage of 9.6Vdc-14Vdc and is ideal for intermediate bus structures where load power (POL) is usually required. They offer very tightly programmable output voltages of 0.7525V to 5.5V. Y-Series converters provide excellent thermal performance even in high temperature environments with minimal airflow. Even in the absence of natural convection airflow, derating to 85°C (for 5 V and 3.3 V outputs, derate to 70°C) is not required. This is achieved through the use of advanced circuitry, packaging and processing techniques to enable designs with ultra-high efficiency, superior thermal management and an extremely low body profile. The low body profile and exclusion of heat sinks minimize system airflow resistance, enhancing cooling of upstream and downstream equipment. The use of 100% automated assembly, coupled with advanced power electronics and thermal design, makes the product extremely reliable.

Operating Input and Output Impedance Y-Series converters should be connected to a DC power source through low impedance. In many applications, the inductance associated with the distribution from the power supply to the input of the converter can affect the stability of the converter. It is recommended to use a decoupling capacitor as close as possible to the input of the converter (minimum 47µF) to ensure converter stability and reduce input ripple voltage. Internally, the converter has an input capacitance of 10µF (low ESR ceramic). In typical applications, low ESR tantalum or POS capacitors are sufficient to provide adequate ripple voltage filtering at the input of the converter. However, it is recommended to use very low ESR ceramic capacitors 47µf 100µf at the input of the converter to minimize the input ripple voltage. They should be as close as possible to the input of the converter. The YM12S05 is designed for stable operation without external capacitors at the output. It is recommended to install low ESR ceramic capacitors to reduce output ripple voltage. To improve transient performance and reduce output voltage ripple, it is recommended to place low ESR ceramic capacitors as close to the load as possible. Maintaining low resistance and low inductance printed circuit board traces is important for connecting loads to the output pins of the converter. This is to maintain good load regulation, as the converter has no sense pins to compensate for the voltage drop associated with the power distribution system on your PCB.
ON/OFF (Pin 1) The ON/OFF pin (Pin 1) is used to remotely turn the power converter on or off via a system signal referenced to GND (Pin 4).

A typical connection is shown in Figure A. The pin to turn on/off the converter should be at logic low or remain on, and the pin to turn off the converter should be at logic high or connected to VIN. The open/close pin is pulled down internally. TTL or CMOS logic gates, open collector (open drain) transistors can be used to drive the on/off pins. When using open collector (open drain) transistors,
Add a 75K pull-up resistor (R*) to VIN as shown in Figure A.

The device must be able to: - Drop to 0.2 mA at low level voltages ≤ 0.8 V - rise to 0.25 mA at high logic levels of 2.3 V–5 V - rise to 0.75 mA when connected to VIN.

OUTPUT VOLTAGE PROGRAMMING (Pin 3) The output voltage can be programmed from 0.7525V to 5.5V by connecting an external resistor between the trim pin (Pin 3) and the GND pin (Pin 4); see Figure B. Note that when the trimmer resistor is not connected, the output voltage of the converter is 0.7525V. The trimmer resistor, RTRIM, for the desired output voltage can be calculated using the following formula:
0.7525)-(v 5.10r req-o rimt 8722 ;=[kΩ], where,=trimr required trim resistor value[kΩ]=−reqov required (trimmed) output voltage[v]

Note that the tolerance of the trimmer resistor directly affects the output voltage tolerance. Standard 1% or 0.5% resistors are recommended; for tighter tolerances, two resistors in parallel are recommended instead of one of the standard values in Table 1.

The ground pin of the trimmer resistor should be connected directly to the ground pin of the converter with no voltage drop in between. Table 1 provides trimmer resistor values for common output voltages.
The output voltage can also be programmed via an external voltage source. To reduce trimming sensitivity, it is recommended to use an external resistor REXT in series between the trimming pin and the programming voltage source. The formula for calculating the control voltage is:
15 0.7525)-)(VR1(7.0V req-oext ctrl+−=[V] where = ctrl v control voltage [V] = external resistor between trim pin and voltage source; can be adjusted according to desired output voltage range [ KΩ] select this value. Table 2 shows the control voltages, where =External 0 and =External 15K.

Protection Function Input Under-Voltage Lockout Input under-voltage lockout is standard on this converter. When the input voltage falls below a predetermined voltage, the converter will shut down; when VIN returns to the specified range, the converter will automatically start. The input voltage must typically be 9.0V for the converter to turn on. Once the converter is turned on, it will turn off when the input voltage drops below 8.8V.
Output Overcurrent Protection (OCP): The converter is protected against overcurrent and short circuits. Once an overcurrent condition is detected, the converter will enter hiccup mode. Once the overload or short-circuit condition is removed, VOUT will return to its rated value. The Over Temperature Protection (OTP) converter will shut down in over temperature conditions to protect itself from overheating due to operation outside the thermal derating curve or operation under abnormal conditions such as system fan failure. After the drive has cooled to a safe operating temperature, it will restart automatically.
Safety Requirements According to UL60950 and EN60950, the converter complies with North American and international safety regulations. Under all operating conditions, the maximum DC voltage between any two pins is VIN. Therefore, the device has an ELV (Extra Low Voltage) output, meeting SELV requirements with all input voltages being ELV. The converter has no internal fuse. To comply with safety agency requirements, a recognized fuse with a maximum rating of 7.5 amps must be used in series with the input line.
Characterizes many operational aspects of general information converters, including vertical and horizontal mounting, efficiency, thermal derating at startup and shutdown (maximum load current as a function of ambient temperature and airflow)

parameters, output ripple and noise, transient response to load step changes, overloads and short circuits. The numbers are numbered as shown in figure XY, where X represents different output voltages and Y represents a specific figure (Y=1 for vertical thermal derating, …). For example, Figure X.1 will refer to vertical thermal derating of all output voltages. The following pages contain specific plots or waveforms associated with the converter. Additional notes on specific data are provided below. Test Conditions: All data using converters soldered on test boards, specifically 0.060" thick four-layer printed wiring boards (PWB). No metallization on top and bottom layers. The two inner layers consist of two ounces of copper, with to provide traces to connect to the converter. No metallization on the outer layers and limited thermal connection ensures that heat transfer from the converter to the PWB is minimized. This provides a worst-case but consistent solution for thermal derating. All airflow required The measurements were made in both vertical and horizontal wind tunnel facilities, using infrared (IR) thermal imaging cameras and thermocouples for temperature measurements. It is important to ensure that components on the converter do not exceed their ratings to maintain high reliability. If If the converter is expected to be operated at or near the maximum load specified in the derating curve, care should be taken to check the actual operating temperature in the application. Thermal imaging is best; if this capability is not available, a thermocouple can be used. AWG 40 gauge thermocouples are recommended to ensure measurement accuracy. Careful placement of thermocouple leads will further reduce measurement errors.

The graph shows thermally derated load current as a function of ambient temperature and airflow rate. X.1 to X.2, maximum temperature 120°C. Ambient temperature varies from 25°C to 85°C, airflow velocities from 30 to 500 LFM (0.15 m/s to 2.5 m/s), vertical and horizontal mounting of converters. For each set of conditions, the maximum load current is defined as the lowest of: (i) the output current at which any MOSFET temperature does not exceed the maximum specified temperature (120°C) shown in the thermal image, or (ii) the converter during normal operation The maximum rated current (5a), the maximum iron derating curve temperature shall not exceed 120°C. To operate within the derating curve, the printed circuit board temperature at the thermocouple location shown in Figure C should not exceed 120°C. Efficiency graph X.3 shows a graph of efficiency versus load current at 25°C ambient temperature, 200 LFM (1 m/s) airflow rate and input voltages of 9.6V, 12V and 14V. Power dissipation graph X.4 shows the power dissipation vs. load current graph for Ta=25°C, 200 LFM (1 m/s) airflow rate (vertical installation) and 9.6V, 12V and 14V. Ripple and Noise The output voltage ripple waveform is measured at full rated load current. Note that all output voltage waveforms are measured through 1µF ceramic capacitors. The output voltage ripple and input reflected ripple current waveforms were obtained using the test setup shown in Figure D.