Caravel Analog User

This is the second test chip from the Chipalooza challenge 2024. 14 designs made it on the September tapeout, although many of those were Efabless designs filling in gaps for IP not provided through the Chipalooza challenge.

The projects on this tapeout and their source URLs are as follows:

1.	Power-on-reset
	sky130_sw_ip__bgrref_por
	https://github.com/efabless/sky130_sw_ip__bgrref_por (forked)
	https://github.com/openicdesign/sky130_sw_ip__bgrref_por
	Stephen Wu

2.	Ultra-low-power comparator
	sky130_icrg_ip__ulpcomp
	https://github.com/efabless/sky130_icrg_ip__ulpcomp (forked)
	https://github.com/JYSquare2/sky130_ef_ip__ulpcomp
	ICRG (Lee Jun Yan and team)

3.	MOSFET voltage reference
	sky130_ak_ip__cmos_vref
	https://github.com/efabless/sky130_ak_ip__cmos_vref (forked)
	https://gihub.com/adankvitschal/sky130_ak_ip__cmos_vref
	Adan Kvitschal

4.	LDO
	sky130_am_ip__ldo_01v8
	https://github.com/efabless/sky130_am_ip__ldo_01v8 (forked)
	https://github.com/AlexMenu/sky130_am_ip__ldo_01v8
	Alexandre Menu

5.	Programmable PLL
	sky130_aa_ip__programmable_pll
	https://github.com/efabless/sky130_aa_ip__programmable_pll (forked)
	https://github.com/Azeem-Abbas/Sky130_ef_ip__Programmable_PLL
	Hafiz Azeem Abbas and team

6.	Audio sigma-delta ADC output driver
	sky130_iic_ip__audiodac_v1
	https://github.com/efabless/sky130_iic_ip__audiodac_v1 (forked)
	https://github.com/iic-jku/iic-audiodac-v1
	IIC-JKU (Harald Pretl)

7.	16MHz R-C oscillator
	sky130_ef_ip__rc_osc_16M
	https://github.com/RTimothyEdwards/sky130_ef_ip__rc_osc_16M
	Tim Edwards/Efabless

8.	500MHz R-C oscillator
	sky130_ef_ip__rc_osc_500k
	https://github.com/RTimothyEdwards/sky130_ef_ip__rc_osc_500k
	Tim Edwards/Efabless

9.	8-bit rheostat
	sky130_ef_ip__rheostat_8bit
	https://github.com/RTimothyEdwards/sky130_ef_ip__rheostat_8bit
	Tim Edwards/Efabless

10.	8-bit IDAC
	sky130_ef_ip__biasgen
	https://github.com/RTimothyEdwards/sky130_ef_ip__biasgen
	Tim Edwards/Efabless

11.	8-bit RDAC
	sky130_ef_ip__rdac3v_8bit
	https://github.com/RTimothyEdwards/sky130_ef_ip__rdac3v_8bit
	Tim Edwards/Efabless

12.	Comparator for ADC
	sky130_ef_ip__ccomp3v
	https://github.com/RTimothyEdwards/sky130_ef_ip__ccomp3v
	Tim Edwards/Efabless

13.	Sample-and-hold
	sky130_ef_ip__samplehold
	https://github.com/RTimothyEdwards/sky130_ef_ip__samplehold
	Tim Edwards/Efabless

14.	12-bit CDAC
	sky130_ef_ip__cdac3v_12bit
	https://github.com/RTimothyEdwards/sky130_ef_ip__cdac3v_12bit
	Tim Edwards/Efabless

(Documentation, including test instructions, still needs to be completed)

:---: | :---

Building:

Get the dependencies above by doing "make get_ip_blocks" in the top level directory. This will clone all of the IP blocks from various github repository sources into the "dependencies" directory.

The test chip is generated in magic by running magic in the mag/ directory and issuing the command "source construct_testchip.tcl".

Verifying:

In the top level directory, do "make run-precheck". This requires at least setting environment variables PDK_ROOT, PDK, and PRECHECK_ROOT. If the PDK is installed with open_pdks, then PRECHECK_ROOT can be set to open_pdks/sources/precheck_sky130.

Testing:

All projects are connected either to the logic analyzer (256 I/O bits) or the GPIO pins. Generally speaking, static control bits (enable and trim, for example) are logic analyzer outputs. Dynamic digital bits are routed to GPIO digital outputs, while analog I/O are routed to the analog connections of the GPIO. Each GPIO will need to be configured for digital input, digital output, or analog operation by the program running the test. Because the number of digital outputs exceeds the 128-bit width of the logic analyzer, both "la_data_in" and "la_oenb" lines (which are effectively just additional output bits) have been used.

Unlike the first test chip, this one has a standardized set of multiplexers on the GPIO analog pins, allowing each GPIO pin to access one of two internal analog signals (otherwise, there would not be enough GPIO pins to accommodate all of the test points needed for every analog block). Each multiplexer consists of two isolated switches, each with two control bits, one of which makes the connection and the other of which grounds the center. These bits should never both be enabled (value 1) at the same time; otherwise, the analog signal gets shorted to ground. These are not, strictly speaking, multiplexers; they are two independent switches connected to the same pin. For that reason, both switches should not be enabled at the same time. In the list of analog blocks and their control signals, below, both the controls for the output of the block in question, and the controls for the other analog block connected to the same GPIO.

Each power supply is routed through gated power pFETs so each project can be powered individually. Each power supply connection internally is routed to a bare analog pin for monitoring the supply voltage of the project, for 11 of the 14 projects (because only 11 bare-analog pins are available). Be aware that these are ESD-sensitive points!

Project circuit blocks are described below, starting at the top left corner of the chip and working counterclockwise around the chip perimeter.

8-bit IDAC (Tim Edwards) Enable: la_oenb[35] Bias: Internally self-biased when Reference select = 0 Bias: gpio_analog[17] (pin GPIO 24) set externally to 1.2V nominal when Reference select = 1 Reference select: la_data_in[35] (0 = internal self-bias, 1 = external bias) Upstream analog power supply: vdda2/vssa2 Upstream digital power supply: vccd2/vssd2 Power supply monitor: (none) Power supply enable: la_data_in[47] Digital input: 8-bit value vector is: la_data_in[31], la_oenb[31], la_data_in[32], la_oenb[32], la_data_in[33], la_oenb[33], la_data_in[34], la_oenb[34], Analog output: source out = gpio_noesd[7] (pin GPIO 14) when la_data_in[18] = 0 (no ground shunt) la_oeb[18] = 1 (connect channel) la_data_in[19] = 1 (ground shunt on other channel) la_oeb[19] = 0 (disconnect other channel) sink out = gpio_noesd[8] (pin GPIO 15) when la_data_in[16] = 0 (no ground shunt) la_oeb[16] = 1 (connect channel) la_data_in[17] = 1 (ground shunt on other channel) la_oeb[17] = 0 (disconnect other channel) Analog input: IDAC reference trim: gpio_noesd[10] (pin GPIO 17) when la_data_in[12] = 0 (no ground shunt) la_oeb[12] = 1 (connect channel) la_data_in[13] = 1 (ground shunt on other channel) la_oeb[13] = 0 (disconnect other channel)

LDO (Alexandre Menu)

Enable: la_oenb[30] Bias: Internally self-biased when Reference select = 0 Bias: gpio_analog[17] (pin GPIO 24) set externally to 1.2V nominal when Reference select = 1 Reference select: la_data_in[30] (0 = internal self-bias, 1 = external bias) Upstream analog power supply: vdda2/vssa2 Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[10] (pin GPIO 24) Power supply enable: la_data_in[46] Analog output: voltage out = gpio_noesd[9] (pin GPIO 16) when la_data_in[14] = 0 (no ground shunt) la_oeb[14] = 1 (connect channel) la_data_in[15] = 1 (ground shunt on other channel) la_oeb[15] = 0 (disconnect other channel)

MOSFET voltage reference (Adan Kvitschal)

Enable: la_oenb[27] Upstream analog power supply: vccd2/vssd2 (note this is a 1.8V supply) Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[9] (pin GPIO 23) Power supply enable: la_data_in[45] Trim: la_data_in[28], la_oenb[28], la_data_in[29], la_oenb[29] Analog outputs: vbg reference out = gpio_noesd[8] (pin GPIO 15) when la_data_in[17] = 0 (no ground shunt) la_oeb[17] = 1 (connect channel) la_data_in[16] = 1 (ground shunt on other channel) la_oeb[16] = 0 (disconnect other channel) vbgsc reference out = gpio_noesd[9] (pin GPIO 16) when la_data_in[15] = 0 (no ground shunt) la_oeb[15] = 1 (connect channel) la_data_in[14] = 1 (ground shunt on other channel) la_oeb[14] = 0 (disconnect other channel) vbgtg reference out = gpio_noesd[10] (pin GPIO 17) when la_data_in[13] = 0 (no ground shunt) la_oeb[13] = 1 (connect channel) la_data_in[12] = 1 (ground shunt on other channel) la_oeb[12] = 0 (disconnect other channel) vptat reference out = gpio_noesd[11] (pin GPIO 18) when la_data_in[19] = 0 (no ground shunt) la_oeb[19] = 1 (connect channel) la_data_in[18] = 1 (ground shunt on other channel) la_oeb[18] = 0 (disconnect other channel)

Comparator for ADC (Tim Edwards)

Enable: la_data_in[27] Upstream analog power supply: vdda2/vssa2 Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[8] (pin GPIO 22) Power supply enable: la_data_in[44] Analog output: io_out[17] (pin GPIO 28) Analog inputs: in positive = gpio_noesd[11] (pin GPIO 18) when la_data_in[10] = 0 (no ground shunt) la_oeb[10] = 1 (connect channel) la_data_in[11] = 1 (ground shunt on other channel) la_oeb[11] = 0 (disconnect other channel) in negative = gpio_noesd[12] (pin GPIO 19) when la_data_in[8] = 0 (no ground shunt) la_oeb[8] = 1 (connect channel) la_data_in[9] = 1 (ground shunt on other channel) la_oeb[9] = 0 (disconnect other channel)

12-bit CDAC (Tim Edwards)

Enable: N/A Upstream analog power supply: vdda2/vssa2 Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[7] (pin GPIO 21) Power supply enable: la_data_in[43] Analog inputs: reference high = gpio_noesd[11] (pin GPIO 18) when la_data_in[11] = 0 (no ground shunt) la_oeb[11] = 1 (connect channel) la_data_in[10] = 1 (ground shunt on other channel) la_oeb[10] = 0 (disconnect other channel) reference low = gpio_noesd[12] (pin GPIO 19) when la_data_in[9] = 0 (no ground shunt) la_oeb[9] = 1 (connect channel) la_data_in[8] = 1 (ground shunt on other channel) la_oeb[8] = 0 (disconnect other channel) Analog output: CDAC out = gpio_noesd[13] (pin GPIO 20) when la_data_in[7] = 0 (no ground shunt) la_oeb[7] = 1 (connect channel) la_data_in[6] = 1 (ground shunt on other channel) la_oeb[6] = 0 (disconnect other channel) Digital inputs: reset = la_oenb[26] 12-bit value = la_oenb[20], la_data_in[21], la_oenb[21], la_data_in[22], la_oenb[22], la_data_in[23], la_oenb[23], la_data_in[24], la_oenb[24], la_data_in[25], la_oenb[25], la_data_in[26]

16MHz R-C oscillator (Tim Edwards)

Enable: la_data_in[20] Upstream analog power supply: vdda2/vssa2 Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[6] (pin GPIO 20) Power supply enable: la_data_in[42] Output: io_out[21] (GPIO 21)

Audio sigma-delta ADC output driver (Harald Pretl)

Enable: N/A (As a digital driver, it does not consume power unless driven.) Upstream analog power supply: vccd2/vccd2 (note this is a 1.8V supply) Upstream digital power supply: vccd2/vssd2 Power supply monitor: io_analog[5] (pin GPIO 19) Power supply enable: la_data_in[41] Digital inputs: positive: io_in[26] (GPIO 37) negative: io_in[25] (GPIO 36) Analog outputs: positive: gpio_noesd[16] (pin GPIO 23) when la_data_in[1] = 0 (no ground shunt) la_oeb[1] = 1 (connect channel) la_data_in[0] = 1 (ground shunt on other channel) la_oeb[0] = 0 (disconnect other channel) negative: gpio_noesd[15] (pin GPIO 22) when la_data_in[3] = 0 (no ground shunt) la_oeb[3] = 1 (connect channel) la_data_in[2] = 1 (ground shunt on other channel) la_oeb[2] = 0 (disconnect other channel)

8-bit RDAC (Tim Edwards)

Enable: la_oenb[115] Upstream analog power supply: vdda1/vdda1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: io_analog[0] (pin GPIO 14) Power supply enable: la_data_in[54]

Analog inputs: reference high = gpio_noesd[3] (pin GPIO 18) when la_oeb[123] = 0 (no ground shunt) la_data_in[123] = 1 (connect channel) la_oeb[122] = 1 (ground shunt on other channel) la_data_in[122] = 0 (disconnect other channel) reference low = gpio_noesd[1] (pin GPIO 19) when la_oeb[125] = 0 (no ground shunt) la_data_in[125] = 1 (connect channel) la_oeb[124] = 1 (ground shunt on other channel) la_data_in[124] = 0 (disconnect other channel)

Analog output: RDAC out = gpio_noesd[0] (pin GPIO 16) when la_oeb[126] = 0 (no ground shunt) la_data_in[126] = 1 (connect channel) la_oeb[127] = 1 (ground shunt on other channel) la_data_in[127] = 0 (disconnect other channel) Digital input: la_data_in[115], la_oenb[114], la_data_in[114], la_oenb[113], la_data_in[113], la_oenb[112], la_data_in[112], la_oenb[111]

8-bit rheostat (Tim Edwards)

Enable: N/A Upstream analog power supply: vdda1/vdda1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: io_analog[1] (pin GPIO 15) Power supply enable: la_data_in[53]

Analog inputs: reference high = gpio_noesd[3] (pin GPIO 18) when la_oeb[122] = 0 (no ground shunt) la_data_in[122] = 1 (connect channel) la_oeb[123] = 1 (ground shunt on other channel) la_data_in[123] = 0 (disconnect other channel) reference low = gpio_noesd[1] (pin GPIO 19) when la_oeb[124] = 0 (no ground shunt) la_data_in[124] = 1 (connect channel) la_oeb[125] = 1 (ground shunt on other channel) la_data_in[125] = 0 (disconnect other channel)

Analog output: RDAC out = gpio_noesd[0] (pin GPIO 16) when la_oeb[127] = 0 (no ground shunt) la_data_in[127] = 1 (connect channel) la_oeb[126] = 1 (ground shunt on other channel) la_data_in[126] = 0 (disconnect other channel) Digital input: la_data_in[111], la_oenb[110], la_data_in[110], la_oenb[109], la_data_in[109], la_oenb[108], la_data_in[108], la_oenb[107]

Power-on-reset (Stephen Wu)

Enable: N/A Bias: gpio_analog[17] (pin GPIO 24) set externally to 1.2V nominal Upstream analog power supply: vdda1/vdda1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: io_analog[2] (pin GPIO 16) Power supply enable: la_data_in[52] Digital outputs: por: io_out[7] (GPIO 7) porb: io_out[8] (GPIO 8) porb_h: gpio_noesd[5] (pin GPIO 21) when la_oeb[118] = 0 (no ground shunt) la_data_in[118] = 1 (connect channel) la_oeb[119] = 1 (ground shunt on other channel) la_data_in[119] = 0 (disconnect other channel)

Programmable PLL (Azeem Abbas)

Upstream analog power supply: vccd1/vccd1 (note this is a 1.8V supply) Upstream digital power supply: N/A (single supply) Power supply monitor: N/A Power supply enable: la_data_in[51] Analog I/O: lowpass filter = gpio_noesd[4] (pin GPIO 11) when la_oeb[120] = 0 (no ground shunt) la_data_in[120] = 1 (connect channel) la_oeb[121] = 1 (ground shunt on other channel) la_data_in[121] = 0 (disconnect other channel) fin = gpio_noesd[13] (pin GPIO 20) when la_data_in[6] = 0 (no ground shunt) la_oeb[6] = 1 (connect channel) la_data_in[7] = 1 (ground shunt on other channel) la_oeb[7] = 0 (disconnect other channel) ibias = gpio_noesd[14] (pin GPIO 21) when la_data_in[5] = 0 (no ground shunt) la_oeb[5] = 1 (connect channel) la_data_in[4] = 1 (ground shunt on other channel) la_oeb[4] = 0 (disconnect other channel) vctrl_in = gpio_noesd[15] (pin GPIO 22) when la_data_in[2] = 0 (no ground shunt) la_oeb[2] = 1 (connect channel) la_data_in[3] = 1 (ground shunt on other channel) la_oeb[3] = 0 (disconnect other channel) Digital inputs: S7-S1: la_data_in[100], la_data_in[103], la_oenb[100], la_data_in[101], la_oenb[101], la_data_in[102], la_data_in[104] D19-D12: la_data_in[92], la_oenb[92], la_data_in[93], la_oenb[93], la_data_in[94], la_oenb[94], la_data_in[95], la_oenb[95] D10-D0: la_data_in[106], la_oenb[105], la_data_in[105], la_oenb[104], la_data_in[99], la_oenb[98], la_data_in[98], la_oenb[97], la_data_in[97], la_oenb[96], la_data_in[96] Digital outputs: prescaler: io_out[20] (GPIO 31) up_out: io_out[11] (GPIO 11) dn_out: io_out[12] (GPIO 12) div_out: io_out[15] (GPIO 26) out: io_out[16] (GPIO 27) outb: io_out[14] (GPIO 25) out_usb: io_out[19] (GPIO 30) out_core: io_out[18] (GPIO 29)

Warning: system runs at 1.8V supply but analog pins are not limited; make sure applied voltage does not exceed the 1.8V rail on lowpass filter, fin, ibias, and vctrl_in.

Ultra-low-power comparator (Yun Jan Lee)

Enable: la_data_in[107] Upstream analog power supply: vdda1/vssa1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: io_analog[3] (pin GPIO 17) Power supply enable: la_data_in[50] Analog output: io_out[10] (pin GPIO 10) Analog inputs: in positive = gpio_noesd[4] (pin GPIO 11) when la_oeb[121] = 0 (no ground shunt) la_data_in[121] = 1 (connect channel) la_oeb[120] = 1 (ground shunt on other channel) la_data_in[120] = 0 (disconnect other channel) in negative = gpio_noesd[6] (pin GPIO 13) when la_oeb[116] = 0 (no ground shunt) la_data_in[116] = 1 (connect channel) la_oeb[117] = 1 (ground shunt on other channel) la_data_in[117] = 0 (disconnect other channel) Digital clock: la_oenb[106]

Sample-and-hold (Tim Edwards)

Enable: la_data_in[91] Upstream analog power supply: vdda1/vssa1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: N/A Power supply enable: la_data_in[50] Analog input: sample in = gpio_noesd[5] (pin GPIO 12) when la_oeb[119] = 0 (no ground shunt) la_data_in[119] = 1 (connect channel) la_oeb[118] = 1 (ground shunt on other channel) la_data_in[118] = 0 (disconnect other channel) Analog output: sample out = gpio_noesd[6] (pin GPIO 13) when la_oeb[117] = 0 (no ground shunt) la_data_in[117] = 1 (connect channel) la_oeb[116] = 1 (ground shunt on other channel) la_data_in[116] = 0 (disconnect other channel) Digital hold: la_oenb[91]

500MHz R-C oscillator (Tim Edwards)

Enable: la_oenb[90] Upstream analog power supply: vdda1/vssa1 Upstream digital power supply: vccd1/vssd1 Power supply monitor: io_analog[4] (pin GPIO 18) Power supply enable: la_data_in[48] Output: io_out[13] (GPIO 13)

Loopback test

There is a loopback test connecting two switches that allows the switch resistance (specifically, the resistance of two switches in series), and to measure coupling across a switch when the ground isolation is enabled or disabled.

Analog I/O: loopback 1 = gpio_noesd[14] (pin GPIO 25) when la_data_in[5] = 0 (no ground shunt) la_oeb[5] = 1 (connect channel) la_data_in[4] = 1 (ground shunt on other channel) la_oeb[4] = 0 (disconnect other channel) loopback 2 = gpio_noesd[16] (pin GPIO 27) when la_data_in[0] = 0 (no ground shunt) la_oeb[0] = 1 (connect channel) la_data_in[1] = 1 (ground shunt on other channel) la_oeb[1] = 0 (disconnect other channel)