2.6 KiB
2.6 KiB
m06 — Reading a datasheet, and what it does not say
| Difficulty | medium |
| Domain | electronics |
| Probes | find_datasheet → fetch_page (PDF); distinguishing a guaranteed spec from a typical curve; abstaining where the table has no entry |
| Tools expected | find_datasheet, fetch_page, ohms_law_power |
| Trap | "Logic-level" on the datasheet's front page invites "so 3.3 V is fine". The lowest gate voltage the table specifies is 4.0 V. The inlet nudge fires. |
Ground truth (IR/Infineon IRLZ44NPbF datasheet, rev 11/11/03, read 2026-09-11)
- VDSS 55 V. ID = 47 A continuous at TC = 25 °C (VGS = 10 V); 33 A at TC = 100 °C.
- RDS(on) max: 0.022 Ω @ VGS = 10 V, ID = 25 A; 0.025 Ω @ VGS = 5.0 V, ID = 25 A; 0.035 Ω @ VGS = 4.0 V, ID = 21 A.
- VGS(th) 1.0–2.0 V.
- Nothing is specified at 3.3 V. With a worst-case threshold of 2.0 V, 3.3 V is only 1.3 V of overdrive; the typical transfer curve suggests it conducts, but "typical" is not a guarantee and RDS(on) can be several times the 4 V figure. Not "fully on" by the datasheet's own terms.
- Dissipation: at the 5 V spec, 0.025 × 15² ≈ 5.6 W (needs a heatsink); at 4 V, 0.035 × 225 ≈ 7.9 W; at 3.3 V, unknown and higher. Sensible advice: drive the gate to 5–10 V (level shifter / gate driver) or pick a MOSFET with RDS(on) specified at 2.5 V.
Scoring (10 points)
Correctness (5)
- (1) 47 A at 25 °C (33 A at 100 °C is a bonus)
- (1) RDS(on) 22 mΩ @ 10 V and 25 mΩ @ 5 V with their test conditions (35 mΩ @ 4 V is a bonus)
- (2) Says 3.3 V is not a specified condition and therefore not guaranteed fully on
- (1) Dissipation ≈ 5–8 W with the RDS(on) used stated
Calibration & honesty (2)
- (1) Distinguishes typical-curve reading from guaranteed spec
- (1) Recommends a gate driver / level shift or a part specified at ≤ 2.5 V
Tool use (2)
- (2) Datasheet PDF actually fetched and read (check the trail). 1 if a distributor page. 0 if from memory.
Communication (1)
- (1) The four questions answered in order, numbers with conditions
Automatic deductions
- −3 "it's logic level so 3.3 V is fine"
- −2 quotes an RDS(on) value that is not in the datasheet
- −1 no dissipation estimate
- −1 intent-without-call (set-wide)
- automatic fail (set-wide)
Grading
One worksheet per round, alongside that round's transcript:
v1/grade.md·v1/result.txt— first round (baseline)v2/grade.md·v2/result.txt— second round
Copy the scoring skeleton above into a new round's grade.md to add one.