UC2845B
Every spec below is cited to the manufacturer datasheet. Compare the closest alternatives, then ask the assistant what it means for your design.
What the UC2845B does
The UC284x/384x family comprises high-performance current mode PWM controllers available in UC2842B through UC2845B and UC3842B through UC3845B variants. These devices feature a trimmed oscillator guaranteed at 250kHz with operation extending to 500kHz, a 5V reference, and a high-current totem pole output capable of sourcing or sinking 1A. The family supports automatic feed-forward compensation, latched PWM for cycle-by-cycle current limiting, and an internally trimmed reference with under-voltage lockout. Typically used for off-line or DC to DC fixed frequency control schemes, these controllers minimize external parts while driving N-Channel MOSFETs efficiently.
Datasheet parameters
| Parameter | Min | Typ | Max | Conditions | Source |
|---|---|---|---|---|---|
| quiescent current | — | 12 mA | 17 mA | VPIN2 = VPIN3 = 0V; ii; TOTAL STANDBY CURRENT | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| output voltage | 4.95 V | 5 V | 5.05 V | Tj = 25°C Io = 1mA; vref; REFERENCE SECTION | ST datasheet, p. 3 — ORDERING NUMBERS |
| supply voltage range | 9 V | 10 V | 11 V | X842B/4B; UNDER-VOLTAGE LOCKOUT SECTION | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| switching frequency | — | 52 kHz | — | RT = 6.2k, CT = 1nF, Tj = 25 °C | ST datasheet, p. 3 — ORDERING NUMBERS |
| gain bandwidth | 700 kHz | 1 MHz | — | TJ = 25°C; ERROR AMP SECTION | ST datasheet, p. 3 — ORDERING NUMBERS |
| operating temperature | -25 °C | — | 85 °C | UC284XB | ST datasheet, p. 3 |
| power dissipation (abs max) | — | — | 1.25 W | ptot(minidip); ABSOLUTE MAXIMUM RATINGS | ST datasheet, p. 2 — ABSOLUTE MAXIMUM RATINGS |
| standby current | — | 300 µA | 500 µA | Vi = 6.5V for UCX843B/45B; TOTAL STANDBY CURRENT | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| psrr | 60 dB | 70 dB | — | 12V ≤ Vi≤ 25V; psrr; ERROR AMP SECTION | ST datasheet, p. 3 — ORDERING NUMBERS |
| rise time | — | 50 ns | 150 ns | Tj = 25°C CL = 1nF (2); tr; OUTPUT SECTION | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| fall time | — | 50 ns | 150 ns | Tj = 25°C CL = 1nF (2); tf; OUTPUT SECTION | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| output noise voltage | — | 50 µV | — | 10Hz ≤ f ≤ 10KHz Tj = 25°C (note 2); en; REFERENCE SECTION | ST datasheet, p. 3 — ORDERING NUMBERS |
| zener voltage | 30 V | 36 V | — | Ii = 25mA; viz; TOTAL STANDBY CURRENT | ST datasheet, p. 4 — ELECTRICAL CHARACTERISTICS (continued) |
| output count | — | 1 | — | ST datasheet, p. 2 — PIN FUNCTIONS |
Closest matches to UC2845B
Frequently asked questions
What is the fall time (tf) of the output section at Tj = 25°C with CL = 1nF?
The fall time is 50 ns.
What is the gain bandwidth of the UC2845B under the condition TJ = 25°C; ERROR AMP SECTION?
The gain bandwidth is 1 MHz.
What is the operating temperature for the UC284XB?
The operating temperature is 85 °C.
What is the output count for the UC2845B?
The output count is 1.
What is the output noise voltage of the UC2845B in the reference section?
The output noise voltage is 50 µV for 10Hz ≤ f ≤ 10KHz at Tj = 25°C.
What is the output voltage of the UC2845B at Tj = 25°C Io = 1mA; vref; REFERENCE SECTION?
The output voltage is 5 V.
What is the power dissipation for the UC2845B in a MiniDIP package under Absolute Maximum Ratings?
The power dissipation is 1.25 W.
What is the PSRR of the ERROR AMP SECTION when 12V ≤ Vi≤ 25V?
The PSRR is 70 dB.
What is the quiescent current when VPIN2 = VPIN3 = 0V?
The quiescent current is 12 mA, which represents the total standby current.
What is the rise time of the output section?
The rise time is 50 ns at Tj = 25°C with CL = 1nF.
What is the total standby current when Vi = 6.5V for UCX843B/45B?
The total standby current is 300 µA.
What is the supply voltage range for the UC2845B under-voltage lockout section?
The supply voltage range is 10 V for the X842B/4B under-voltage lockout section.