The LM34926 regulator features all of the functions needed to implement a low-cost, efficient, isolated bias regulator. This high-voltage regulator contains two 100-V N-channel MOSFET switches — a high-side buck switch and a low-side synchronous switch. The constant on-time (COT) control scheme employed in the LM34926 requires no loop compensation and provides excellent transient response. The regulator operates with an on-time control that is inversely proportional to the input voltage. This feature allows the operating frequency to remain relatively constant. An intelligent peak current limit is implemented with integrated sense circuit. Other features include a programmable input undervoltage comparator to inhibit operation during low-voltage conditions. Protection features include thermal shutdown and VCC Undervoltage Lockout (UVLO). The LM34926 device is offered in WSON-8 and SO PowerPAD-8 plastic packages.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM34926 | HSOP (8) | 4.89 mm × 3.90 mm |
WSON (8) | 4.00 mm × 4.00 mm |
Changes from E Revision (December 2014) to F Revision
Changes from D Revision (December 2013) to E Revision
Changes from C Revision (December 2013) to D Revision
Changes from B Revision (March 2013) to C Revision
Changes from A Revision (March 2013) to B Revision
Changes from * Revision (March 2013) to A Revision
PIN | I/O | DESCRIPTION | APPLICATION INFORMATION | |
---|---|---|---|---|
NO. | NAME | |||
1 | RTN | – | Ground | Ground connection of the integrated circuit. |
2 | VIN | I | Input Voltage | Operating input range is 7.5 V to 100 V. |
3 | UVLO | I | Input Pin of Undervoltage Comparator | Resistor divider from VIN to UVLO to GND programs the undervoltage detection threshold. An internal current source is enabled when UVLO is above 1.225 V to provide hysteresis. When UVLO pin is pulled below 0.66 V externally, the parts goes in shutdown mode. |
4 | RON | I | On-Time Control | A resistor between this pin and VIN sets the switch on-time as a function of VIN. Minimum recommended on-time is 100 ns at max input voltage. |
5 | FB | I | Feedback | This pin is connected to the inverting input of the internal regulation comparator. The regulation level is 1.225 V. |
6 | VCC | O | Output from the Internal High Voltage Series Pass Regulator. Regulated at 7.6 V. |
The internal VCC regulator provides bias supply for the gate drivers and other internal circuitry. A 1.0-μF decoupling capacitor is recommended. |
7 | BST | I | Bootstrap Capacitor | An external capacitor is required between the BST and SW pins (0.01-μF ceramic). The BST pin capacitor is charged by the VCC regulator through an internal diode when the SW pin is low. |
8 | SW | O | Switching Node | Power switching node. Connect to the output inductor and bootstrap capacitor. |
– | EP | – | Exposed Pad | Exposed pad must be connected to RTN pin. Connect to system ground plane on application board for reduced thermal resistance. |
MIN | MAX | UNIT | |
---|---|---|---|
VIN, UVLO to RTN | –0.3 | 100 | V |
SW to RTN | –1.5 | VIN + 0.3 | V |
SW to RTN (100-ns transient) | –5 | VIN + 0.3 | V |
BST to VCC | 100 | V | |
BST to SW | 13 | V | |
RON to RTN | –0.3 | 100 | V |
VCC to RTN | –0.3 | 13 | V |
FB to RTN | –0.3 | 5 | V |
Maximum junction temperature(3) | 150 | °C | |
Storage temperature, Tstg | –55 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±2000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±750 |
MIN | MAX | UNIT | |
---|---|---|---|
VIN voltage | 7.5 | 100 | V |
Operating junction temperature(1) | –40 | 125 | °C |
THERMAL METRICS(1) | LM34926 | UNIT | |||
---|---|---|---|---|---|
NGU (WSON) | DDA (SO PowerPAD) | ||||
8 PINS | 8 PINS | ||||
RθJA | Junction-to-ambient thermal resistance | 41.3 | 41.1 | °C/W | |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | 3.2 | 2.4 | °C/W | |
ΨJB | Junction-to-board thermal characteristic parameter | 19.2 | 24.4 | °C/W | |
RθJB | Junction-to-board thermal resistance | 19.1 | 30.6 | °C/W | |
RθJC(top) | Junction-to-case (top) thermal resistance | 34.7 | 37.3 | °C/W | |
ΨJT | Junction-to-top thermal characteristic parameter | 0.3 | 6.7 | °C/W |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
VCC SUPPLY | ||||||
VCC Reg | VCC Regulator Output | VIN = 48 V, ICC = 20 mA | 6.25 | 7.6 | 8.55 | V |
VCC Current Limit | VIN = 48 V(2) | 26 | mA | |||
VCC UVLO Threshold (VCC increasing) | 4.15 | 4.5 | 4.9 | V | ||
VCC UVLO Hysteresis | 300 | mV | ||||
VCC Drop Out Voltage | VIN = 8 V, ICC = 20 mA | 2.3 | V | |||
IIN Operating Current | Nonswitching, FB = 3 V | 1.75 | mA | |||
IIN Shutdown Current | UVLO = 0 V | 50 | 225 | µA | ||
UNDERVOLTAGE SENSING FUNCTION | ||||||
UV Threshold | UV Rising | 1.19 | 1.225 | 1.26 | V | |
UV Hysteresis Input Current | UV = 2.5 V | –10 | –20 | -29 | µA | |
Remote Shutdown Threshold | Voltage at UVLO Falling | 0.32 | 0.66 | V | ||
Remote Shutdown Hysteresis | 110 | mV | ||||
REGULATION AND OVERVOLTAGE COMPARATORS | ||||||
FB Regulation Level | Internal Reference Trip Point for Switch ON | 1.2 | 1.225 | 1.25 | V | |
FB Overvoltage Threshold | Trip Point for Switch OFF | 1.62 | V | |||
FB Bias Current | 60 | nA | ||||
SWITCH CHARACTERISTICS | ||||||
Buck Switch RDS(ON) | ITEST = 200 mA, BST-SW = 7 V | 0.8 | 1.8 | Ω | ||
Synchronous RDS(ON) | ITEST = 200 mA | 0.45 | 1 | Ω | ||
Gate Drive UVLO | VBST − VSW Rising | 2.4 | 3 | 3.6 | V | |
Gate Drive UVLO Hysteresis | 260 | mV | ||||
CURRENT LIMIT | ||||||
Current Limit Threshold | 390 | 575 | 750 | mA | ||
Current Limit Response Time | Time to Switch Off | 150 | ns | |||
OFF-Time Generator (Test 1) | FB = 0.1 V, VIN = 48 V | 12 | µs | |||
OFF-Time Generator (Test 2) | FB = 1.0 V, VIN = 48 V | 2.5 | µs | |||
THERMAL SHUTDOWN | ||||||
Tsd | Thermal Shutdown Temperature | 165 | °C | |||
Thermal Shutdown Hysteresis | 20 | °C |
MIN | TYP | MAX | UNIT | |||
---|---|---|---|---|---|---|
ON-TIME GENERATOR | ||||||
TON Test 1 | VIN = 32 V, RON = 100 kΩ | 270 | 350 | 460 | ns | |
TON Test 2 | VIN = 48 V, RON = 100 kΩ | 188 | 250 | 336 | ns | |
TON Test 3 | VIN = 75 V, RON = 250 kΩ | 250 | 370 | 500 | ns | |
TON Test 4 | VIN = 10 V, RON = 250 kΩ | 1880 | 3200 | 4425 | ns | |
MINIMUM OFF-TIME | ||||||
Minimum Off-Timer | FB = 0 V | 144 | ns |