ZHCSIQ5A September 2018 – August 2021 LM34936
PRODUCTION DATA
Figure 5-1 QFN-28RHF PackageTop View| PIN | DESCRIPTION | ||
|---|---|---|---|
| NO. | NAME | ||
| 1 | MODE | 1.38 V < MODE < 2.22 V : CCM, Hiccup Enabled (Set RMODE resistor to AGND = 93.1 k?). 2.6 V < MODE < VCC: CCM, Hiccup Disabled (Set RMODE resistor to AGND = 200 k? or connect to VCC) | |
| 2 | DITH | A capacitor connected between the DITH pin and AGND is charged and discharged with a current source. As the voltage on the DITH pin ramps up and down the oscillator frequency is modulated by 10% of the nominal frequency set by the RT resistor. Grounding the DITH pin will disable the dithering feature. In the external Sync mode, the DITH pin voltage is ignored. | |
| 3 | RT/SYNC | Switching frequency programming pin. An external resistor is connected to the RT/SYNC pin and AGND to set the switching frequency. This pin can also be used to synchronize the PWM controller to an external clock. | |
| 4 | SLOPE | A capacitor connected between the SLOPE pin and AGND provides the slope compensation ramp for stable current mode operation in both buck and boost mode. | |
| 5 | SS | Soft-start programming pin. A capacitor between the SS pin and AGND pin programs soft-start time. | |
| 6 | COMP | Output of the error amplifier. An external RC network connected between COMP and AGND compensates the regulator feedback loop. | |
| 7 | AGND | Analog ground of the IC. | |
| 8 | FB | Feedback pin for output voltage regulation. Connect a resistor divider network from the output of the converter to the FB pin. | |
| 9 | VOSNS | VOUT sense input. Connect to the power stage output rail. | |
| 10 11 |
ISNS(–) ISNS(+) |
Input or Output Current Sense Amplifier inputs. An optional current sense resistor connected between ISNS(+) and ISNS(–) can be located either on the input side or on the output side of the converter. If the sensed voltage across the ISNS(+) and ISNS(-) pins reaches 50 mV, a slow Constant Current (CC) control loop becomes active and starts discharging the soft-start capacitor to regulate the drop across ISNS(+) and ISNS(-) to 50 mV. Short ISNS(+) and ISNS(-) together to disable this feature. | |
| 12 | CSG | The negative or ground input to the PWM current sense amplifier. Connect directly to the low-side (ground) of the current sense resistor. | |
| 13 | CS | The positive input to the PWM current sense amplifier. | |
| 14 | PGOOD | Power Good open drain output. PGOOD is pulled low when FB is outside a -9%/+10% regulation window around the 0.8-V VREF. | |
| 15 25 |
SW2 SW1 |
The boost and the buck side switching nodes respectively. | |
| 16 24 |
HDRV2 HDRV1 |
Output of the high-side gate drivers. Connect directly to the gates of the high-side MOSFETs. | |
| 17 23 |
BOOT2 BOOT1 |
An external capacitor is required between the BOOT1, BOOT2 pins and the SW1, SW2 pins respectively to provide bias to the high-side MOSFET gate drivers. | |
| 18 22 |
LDRV2 LDRV1 |
Output of the low-side gate drivers. Connect directly to the gates of the low-side MOSFETs. | |
| 19 | PGND | Power ground of the IC. The high current ground connection to the low-side gate drivers. | |
| 20 | VCC | Output of the VCC bias regulator. Connect capacitor to ground. | |
| 21 | BIAS | Optional input to the VCC bias regulator. Powering VCC from an external supply instead of VIN can reduce power loss at high VIN. For VBIAS > 8 V, the VCC regulator draws power from the BIAS pin. | |
| 26 | EN/UVLO | Enable pin. For EN/UVLO < 0.4 V, the LM34936 is in a low current shutdown mode. For EN/UVLO > 1.22 V, the PWM function is enabled, provided VCC exceeds the VCC UV threshold. | |
| 27 | VIN | The input supply pin to the IC. Connect VIN to a supply voltage between 4.2 V and 30 V. | |
| 28 | VISNS | VIN sense input. Connect to power stage input rail. | |
| - | PowerPAD? | The PowerPAD should be soldered to the analog ground. If possible, use thermal vias to connect to a PCB ground plane for improved power dissipation. | |