Answer: The CJT1117B-ADJ is JSCJ’s adjustable 1 A LDO in SOT-223. Two conditions decide whether it fits: the adjustable output is specified only from 1.25 V to 5 V, and JSCJ recommends R1 ≤ 170 Ω so the divider meets the minimum operating current. Within those limits it holds 1.25 V OUT-to-ADJ and drops out at 1.30 V max at 1 A. (JSCJ CJT1117B Rev. 2.3, pp.1–4.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Adjustable output range | 1.25 V to 5 V | With two external resistors | p.1 General Description |
| Reference voltage | 1.231 / 1.250 / 1.269 V | IOUT = 10 mA, VIN = 3.23 V, TJ = 25 °C | p.3 Electrical Characteristics |
| Reference voltage, load & line | 1.225 / 1.250 / 1.275 V | 10 mA ≤ IOUT ≤ 1 A, 2.75 V ≤ VIN − VOUT ≤ 13.25 V, TJ = 25 °C | p.3 |
| Dropout voltage | 1.10 / 1.13 / 1.15 V typ; 1.30 V max at 1 A | IOUT = 100 / 500 / 1000 mA, ΔVREF = 1 % | p.3 |
| Current limit | 1.20 min / 1.50 typ A | VIN − VOUT = 1.5 V | p.3 |
| Minimum load current | 2 typ / 7 max mA | VIN = 5 V, VADJ = 0 V | p.3 |
| Recommended R1 | ≤ 170 Ω | To meet the minimum operating current (ADJ version) | p.4 Typical Application Circuit |
| Adjust pin current | 60 typ / 120 max µA | IOUT = 10 mA | p.3 |
| Line / load regulation (ADJ) | 0.2 % max / 0.4 % max | Line: IOUT 10 mA, 1.5–12 V headroom; load: 1.5 V headroom, 10 mA–1 A | p.3 |
| Ripple rejection | 60 min / 75 typ dB | 120 Hz, COUT 22 µF tantalum, VIN − VOUT 3 V, IOUT 1 A | p.3 |
| Input voltage | 15 V recommended; 20 V absolute max | — | p.2 Recommended Operating Conditions; Absolute Maximum Ratings |
| Temperature | TJ −40 to +125 °C; TA −40 to +85 °C | Recommended operating | p.2 |
| Thermal resistance | RθJA 100 °C/W, RθJC 20 °C/W | Still air, 1 in² FR-4, 2 oz copper | p.2 Thermal Metric |
| Thermal shutdown | 160 °C, 25 °C hysteresis | — | p.3 |
| ESD | HBM 2000 V, MM 400 V | — | p.2 ESD Ratings |
Pinout (SOT-223)
| Pin | Function |
|---|---|
| 1 | ADJ / GND |
| 2 | OUTPUT |
| 3 | IN |
Source: p.1. This is the same pin order as the AMS1117, LM1117 and LD1117. JSCJ’s front page does not label the tab, so this page makes no claim about it.
The two conditions, worked through
1. Output no higher than 5 V. JSCJ describes the adjustable version as covering 1.25 V to 5 V (p.1). A 9 V or 12 V divider is outside what the datasheet describes, even if the resistor maths works.
2. R1 ≤ 170 Ω. The divider has to supply the minimum operating current; JSCJ puts the ceiling at 170 Ω (p.4). The arithmetic matches the 7 mA maximum minimum-load figure: 1.25 V / 170 Ω = 7.35 mA.
Example for 5.0 V with R1 = 150 Ω:
- R2 = 150 × (5.0/1.25 − 1) = 450 Ω (nearest E96 value: 453 Ω).
- With IADJ = 60 µA typical: VOUT = 1.25 × (1 + 453/150) + 60 µA × 453 Ω = 5.025 + 0.027 ≈ 5.05 V.
- Divider current 1.25/150 = 8.3 mA, which is above the 7 mA maximum.
For other resistor pairs, the AMS1117-ADJ calculator uses the same 1.25 V reference; keep its R1 at or below 170 Ω.
Design notes
- Everything is specified at 25 °C. The electrical table header reads “VIN ≤ 10 V, TJ = 25 °C, unless otherwise specified” (p.3), and no row gives over-temperature limits. AMS, TI and ST all publish full-range rows. If you need guaranteed drift limits, this datasheet does not provide them.
- The tight reference band assumes 2.75 V of headroom. The 1.225–1.275 V band (±2 %) is specified for 2.75 V ≤ VIN − VOUT ≤ 13.25 V (p.3). With only 1.5 V of headroom you have the line and load regulation rows, not that band.
- Current. JSCJ specifies dropout up to 1 A (1.30 V max) and a current limit of 1.20 A minimum (p.3), a step up from the AMS1117’s 0.8 A dropout spec.
- Heat. 100 °C/W on 1 in² of 2 oz copper (p.2). From 5 V to 3.3 V at 0.5 A: 0.85 W × 100 = 85 °C rise. Note the 85 °C maximum ambient in the recommended conditions (p.2).
- Ripple. 75 dB typical at 120 Hz with 22 µF tantalum on the output (p.3).
Pitfalls specific to CJT1117B-ADJ
- A 9 V or 12 V output. Outside the 1.25–5 V adjustable range on p.1. Use a different regulator.
- R1 = 240 Ω (LM317 habit) or 200 Ω. Both exceed the 170 Ω recommendation. 240 Ω delivers only 5.2 mA.
- Assuming −40 to 85 °C performance from 25 °C numbers. The temperature range is a rating; the accuracy figures are 25 °C values.
- Reading the marking as the part number. The top mark is “CJT1117B” over “X.X YY”, where X.X is the output voltage and YY is a two-letter weekly production code (p.1).
Part numbers (information only)
JSCJ lists CJT1117B-ADJ, -1.8, -2.5, -3.3 and -5.0, all in SOT-223 for −40 to 125 °C junction temperature (p.2 Ordering Information). Packing is 2,500 pieces per 13-inch reel (p.8).
FAQ
- Can the CJT1117B-ADJ output 9 V or 12 V? No. JSCJ specifies the adjustable version for 1.25 V to 5 V (p.1).
- Why must R1 be 170 Ω or less? So the divider current meets the minimum operating current (p.4). 1.25 V / 170 Ω ≈ 7.35 mA, just above the 7 mA maximum minimum load (p.3).
- Is the CJT1117B-ADJ a drop-in for the AMS1117? For SOT-223 boards with outputs up to 5 V and R1 ≤ 170 Ω, yes; the pin order is the same. See the equivalents comparison for details.
- How much current can it supply? It is rated 1 A, with dropout specified up to 1 A and a 1.20 A minimum current limit (p.3). In SOT-223, heat usually limits you first.
- Does the datasheet give specs over temperature? No. The electrical characteristics are at TJ = 25 °C (p.3); only the operating ranges extend to −40/125 °C junction and −40/85 °C ambient (p.2).
Related (internal links)
- AMS1117 equivalents comparison
- AMS1117-ADJ (SOT-223)
- LM1117MP-ADJ/NOPB
- AMS1117-ADJ resistor calculator
- E-series resistor values
- Voltage dividers
- Linear voltage regulators
Sources (retrieved 2026-10-26)
- Jiangsu Changjing Electronics Technology (JSCJ), CJT1117B-XXX 1A Low Dropout Linear Regulator, Rev. 2.3: https://www.jscj-elec.com/pdf/612dc6a092812e48be7965561183468a.pdf
Disclaimer
Values are copied from JSCJ CJT1117B Rev. 2.3, read on 26 Oct 2026; worked numbers are our arithmetic. Verify against the current datasheet before production.
Reviewed by: Jasper · Updated: 2026-10-26